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Present work reports a systematic study on the evaluation of magnetic inhomogeneities in non-stoichiometric Mg 0·5 Ca 0·5 Fe 2 O 4 nanoferrite (MCNF) by conducting exhaustive dc-magnetization, ac-susceptibility and 57Fe Mössbauer spectroscopic measurements and exchange bias investigations using training protocol down to 6 K. Rietveld fitting to PXRD established the formation of anticipated spinel fcc phase of MCNF (non-stoichiometric) along with a minute impurity phase of calcite. Scherrer method and HRTEM micrographs illustrated broad size distribution of MCNF nanoparticles with an average nanocrystallite size of ∼15 nm. Combined 57Fe Mössbauer spectroscopic and dc-magnetization analysis establishes coexistence of ferrimagnetic (67 %) & superparamagnetic (33 %) states at 300 K with notable M s = 22 emu/g, M r = 4 emu/g & H c = 130 Oe and blocking of most of the nanoparticles of MCNF below 300 K. The coercivity followed the size-modified Kneller law for ferrimagnetic nanoparticles and the saturation magnetization abides the Bloch law. Moreover the frequency-dependent ac-susceptibility investigations revealed two magnetic transitions: (i) A transition at ∼ 330 K in the low frequency data attributed to the relaxation of blocked particles of bigger sizes under the superparamagnetic (SPM) regime and (ii) an irregularity at low temperatures is assigned to surface spin glass freezing. Surface spin glass freezing was further affirmed by the ageing experiments and dynamic scaling law. Furthermore, even the best fit to the dynamic scaling couldn't assert the existence of conventional spin glass phase due to slower spin-flip time of surface spins. A soft ferrimagnetic core of MCNF is enveloped with disordered surface spins, which manifest spin glass state. Concurrently, the findings of exchange bias at 30 K and training effect at 6 K affirmed that MCNF nanoparticles are presenting themselves as FM core- SG shell system. Our experimental findings suggested magnetic inhomogeneities comprised of superparamagnetism, ferrimagnetism and disordered surface spin glass state in the non-stoichiometric MCNF. [ABSTRACT FROM AUTHOR]

A series of La3+ ion doped magnesium nickel ferrites, Mg 0.5 Ni 0.5 Fe 2-x La x O 4 (0 ≤ x ≤ 0.1) having a cubic spinel structure were prepared by the co-precipitation method. Various characterization techniques, including X-ray diffractometer (XRD), high resolution transmission electron microscopy (HR-TEM), electron spin resonance (ESR) and vibrating sample magnetometer (VSM) were used to investigate structural and magnetic properties. The average crystallite size decreases and lattice parameter increases with La3+ ion doping and lie in the range of 12–7 nm and 8.347–8.361 Å respectively. Analysis of ESR spectra reveals that, g-value with La3+ ion addition decreases from 2.57 to 2.12. The saturation magnetization and the coercivity decrease with increasing rare-earth content. Magnetic-hysteresis (M − H) loop shifts from a ferromagnetic to a superparamagnetic nature with La3+ ion addition. The dielectric study was carried out in the frequency range of 1 KHz to 4000 KHz and temperature ranging 30 °C–350 °C using the impedance analyzer. The dielectric constant decreases with increasing frequency and the La3+ ion concentration. The dielectric loss of the sample increases with increasing temperature. The magnetic properties of the synthesized nanoparticles make them a potential material for stable ferrofluid application and the low tangent loss value makes these material a potential candidate for frequency-based applications. [ABSTRACT FROM AUTHOR]

We report a new cancer imaging modality in the contrast of tissue intrinsic susceptibility property by computed inverse magnetic resonance imaging (CIMRI). In MRI physics, an MRI signal is formed from tissue magnetism source (primarily magnetic susceptibility χ) through a cascade of MRI-introduced transformations (e.g. dipole-convolved magnetization) involving MRI setting parameters (e.g. echo time). In two-step computational inverse mappings (from phase image to internal fieldmap to susceptibility source), we could remove the MRI transformations and imaging parameters, thereby obtaining χ-depicted cancer images (canχ) from MRI phase images. Canχ is computationally implemented from clinical cancer MRI phase image by CIMRI. As a result of MRI effect removal through computational inverse mappings, the reconstructed χ map (canχ) could provide a new cancerous tissue depiction in contrast of tissue intrinsic magnetism property (i.e. diamagnetism vs paramagnetism) as in an off-scanner state (e.g. in absence of main field B 0). Through retrospective clinical cancer MRI data analysis, we reported on the canχ method in technical details and demonstrated its feasibility of innovating cancer imaging in the contrast of tissue intrinsic paramagnetism/diamagnetism property (in a cancer tissue state free from MRI effect). [ABSTRACT FROM AUTHOR]

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Lanthanum doped magnesium-zinc spinel ferrite samples were synthesized by the simple co-precipitation method with composition M g 0.5 Z n 0.5 F e 2 − x L a x O 4 (x = 0,0.025,0.05,0.075 a n d 0.1). The synthesized ferrite samples were investigated using by powder X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), electron paramagnetic resonance spectroscopy (EPR) and vibrating sample magnetometer (VSM). The effect of the La3+ ion doping on the crystallite size and lattice parameter of the material has been discussed. The crystallite size for all the samples were found to be in the range of 7–12 nm. The percentage porosity and percentage crystallinity of all the samples were found to be in the range of 49–50% and 80–85% respectively. In the frequency region of 400–600 cm−1 two absorption bands attributed to the T d and O h sites of the spinel ferrite have been observed. FTIR band spectra shift from lower to higher region with La3+ ion doping. Agglomeration of the particles is observed in the FE-SEM and HR-TEM images. Additional impurities except carbon are not present in the sample which is confirmed by EDS analysis. EPR analysis shows a decrease in the g-value from 2.18 to 2.12 for the synthesized samples with La3+ ion doping. The resonance field for synthesized sample shifts to higher magnetic field which may be due to ferromagnetic interaction caused by La3+ ion doping. The maximum spin concentration (1.508 × 1021 spin/g) and the relaxation time (4.132 × 10−11 s−1) was observed for the MZL2 composition. Magnetization curve shows the typical superparamagnetic nature of synthesized samples. The calculated squareness value of the synthesized sample refers to the magnetostatic interaction among particles. The obtained coercive field value is low which makes these materials suitable for ferrofluids and hyperthermia treatment applications. [ABSTRACT FROM AUTHOR]

Porous SnO 2 films were successfully prepared using pure tin foils by a convenient electrochemical anodization method in 0.5 M NaOH solutions. Interestingly, the same sample can simultaneously exhibit room temperature ferromagnetism, paramagnetism and diamagnetism. Moreover, the magnetic behavior is related to the direction of the applying magnetic field, showing obvious magnetic anisotropy. A reasonable explanation for this phenomenon was given by analyzing the morphology, magnetic characterization, and spectral analysis of the films, combined with the knowledge of solid physics. This research will be helpful in expanding the application of porous SnO 2 films. [ABSTRACT FROM AUTHOR]

We have investigated structural, optical, magnetic, magnetic induction heating, cytotoxicity and antimicrobial properties of 7% Na doped MgO nanoparticles (Mg 0.93 Na 0.07 O NPs) synthesized by green self-combustion route using fresh lemon juice as capping and reducing agent. PXRD, FESEM, FEG-TEM, SAED, FTIR and PL analysis confirmed formation of highly crystalline single-phase, ∼26(±5)nm sized Mg 0.93 Na 0.07 O NPs in the NaCl type fcc structure. AFM measurements showed agglomeration of grains. Diffuse reflectance analysis demonstrated maximum reflectance change in the UV & blue color region and wide bandgap of ∼4.79eV for Mg 0.93 Na 0.07 O NPs. 240 nm excited PL emission data exhibited broad emission centered at ∼389 nm and oxygen vacancies in the MgO lattice. ESR study also revealed presence of F-center type defects in the MgO lattice.VSM measurements established superparamagnetic character of Mg 0.93 Na 0.07 O NPs along with some signature of d0 type soft ferromagnetic ordering at RT, which can be well understood in BMP model. Heat generation efficiency of Mg 0.93 Na 0.07 O NPs (SAR = 123.5 W/g) is suitable for mild hyperthermia cancer therapy. Mg 0.93 Na 0.07 O NPs showed remarkable antibacterial and antifungal activity against few common pathogens. MIC values of Mg 0.93 Na 0.07 O NPs against gram-positive S. aureus & S. pyogenes, gram negative E. coli bacteria and C. albicans fungi were found to be comparable to standard drugs. In vitro cytotoxicity of Mg 0.93 Na 0.07 O NPs has been tested on normal fibroblast cells and MCF-7 breast cancer cells by MTT assay method, which showed dose dependent response. Findings revealed that cancer cell viability significantly decreases with increasing concentration of Mg 0.93 Na 0.07 O NPs, however these nanoparticles also showed considerable toxic effect on normal cells at higher concentration. Antimicrobial activity and cytotoxicity of Mg 0.93 Na 0.07 O NPs is attributed to generation of ROS on the surface of nanoparticles. This study demonstrates that greenly synthesized Mg 0.93 Na 0.07 O NPs might be suitable for food packaging, bactericide for water purification and biomedical applications. [Display omitted] • Na doped MgO NPs were obtained by green self-combustion synthesis route using fresh lemon juice. • Na doped MgO NPs display superparamagnetism with some signature of d0 type soft ferromagnetic ordering at RT. • The heat generation efficiency of Mg 0.93 Na 0.07 O NPs (SAR = 123.5 W/g) is suitable for mild hyperthermia cancer therapy. • MIC values of Mg 0.93 Na 0.07 O against gram-positive S. aureus & S. pyogenes and gram negative E. coli bacteria are comparable to standard drugs. Mg 0.93 Na 0.07 O NPs exhibit strong antifungal activity against C. albicans fungi. • In vitro cytotoxicity of Mg 0.93 Na 0.07 O NPs has been tested on normal fibroblast cells and MCF-7 breast cancer cells by MTT assay method, which showed dose dependent response. [ABSTRACT FROM AUTHOR]

(In 1-x Er x) 2 O 3 nanoparticles were synthesized by lyophilization of an aqueous solution of indium and erbium acetates and then applying heat treatments. These nanoparticles were characterized regarding their structural, optical, and magnetic properties over a temperature range of 2–300 K. For x ≤ 0.04, all samples were monophasic, crystallized with cubic structure (Ia-3 space group), and characterized by oxygen vacancies. Er doping reduced the crystallite size and increased the lattice strain. However, no change in energy bandgap was observed after erbium dilution in the oxide matrix. The doped samples were paramagnetic over the entire temperature range, but at low temperatures paramagnetism coexisted with a ferromagnetic phase. The ferromagnetism was attributed to the presence of magnetic polarons acting as mediators of the coupling between the Er3+ ions. The low-temperature segments of the magnetization curves, i.e., M(T< 20 K), were successfully fitted based on the Bound Magnetic Polaron model. [Display omitted] • In2-xErxO3 monophasic NPs were successfully synthesized by lyophilization and heat treatments. • The semiconductor In2O3 was for the first doped with a HRE and the solubility limit for Er was 4%at. • Er doping decreased particle size, increased strain, and did not change the semiconductor bandgap. • In2-xErxO3 is PM at and below RT but a FM phase appears at T < 20 K. • The FM phase is due to bound magnetic polarons formed by Er3+ cations. [ABSTRACT FROM AUTHOR]

The core-shell structural Fe 3 O 4 @MBT-LDH was synthesized via the ion exchange method, with MBT (2-mercaptobenzothiazole) inhibitor ions intercalated lamellar ZnAlCe-LDH attaching closely to the Fe 3 O 4 microspheres surface. The morphology, composition, structure, and magnetic properties of the composite were measured by transmission electron microscope, X-ray diffraction, Fourier transform infrared spectra, and vibrating sample magnetometer. The release behavior of MBT ions and corrosion inhibition performance of the Fe 3 O 4 @MBT-LDH under "no MF" (without an external magnetic field) and "MF ON" modes (under an external magnetic field) were measured by UV–vis spectroscopy, electrochemical tests, scanning electron microscopy, and X-ray photoelectron spectrometer (XPS). Calcinating the composite after the release test and redispersing the sintered products in MBT ions-containing solution, the composite was reestablished. Results showed that the Fe 3 O 4 @MBT-LDH possessed moderate MBT loadings amount (12.0%) and presented strong superparamagnetic properties with saturation magnetization (M s) of 27.6 emu⋅g−1. The release behavior of the MBT− from the composite was sustainable and could be further slowed down by using an external magnetic field with changing the release mechanism. The release curve reached equilibrium with a longer time of 48 h and a lower release amount of 57.0% under MF ON mode than that of no MF mode with a time of 7 h and a release amount of 74.7%. The Fe 3 O 4 @MBT-LDH owned a good and long-term protection performance for Q235 carbon steel with maximum corrosion inhibition efficiency (η e) of up to 93.30%. As a promising controlled-release inhibitor, it could be recycled and regenerated by simple treatment, still having high η e higher than 80% and excellent magnetic properties with M s of 21.47 emu⋅g−1 after five cycles. The corrosion mechanism for carbon steel was further analyzed by quantum chemical calculations and molecular dynamics simulation. • The superparamagnetic core-shell structural Fe 3 O 4 @MBT-LDH was synthesized. • The Fe 3 O 4 @MBT-LDH possessed magnetic controlled release properties. • The Fe 3 O 4 @MBT-LDH showed long-term protection performance for Q235 steel. • The Fe 3 O 4 @MBT-LDH could be regenerated and recycled. • The corrosion mechanism was analyzed by theoretical calculations. [ABSTRACT FROM AUTHOR]

The response of arrays of magnetic nanoparticles (MNPs) of cubic anisotropy materials (magnetite or iron) to high-frequency (sub-GHz) field is investigated utilizing micromagnetic simulations. Composites of MNPs embedded in dielectric media are of interest as core materials for high-frequency power microconverters with low eddy-current losses. Going beyond the macrospin approximation for MNPs (including internal spin structure), we simulate the magnetization dynamics of arrays of spherical and periodically arranged MNPs under periodic boundary conditions and in the presence of thermal fluctuations of the magnetization within the stochastic thermal field. Analyzing the dependence of the dynamical response on the size of the MNPs, we find the size to be crucial for exciting regular magnetization oscillations at room temperature and reducing hysteresis loss. The efficiency of the dynamical response of composites of high-magnetization-metal (iron) MNPs is compared to that of magnetite nanocomposites. We find the sub-GHz susceptibility of magnetite-containing nanocomposite to be comparable to that of the iron MNPs despite the lower saturation magnetization of Fe 3 O 4 , (at the volumetric ratio of the magnetic phase of 0.13, susceptibility is χ ≈ 1. 6 for 5 nm Fe and ≈ 1. 4 for 12 nm Fe 3 O 4 MNPs at T = 300 K and frequency of 0.1 GHz). • Arrays of superparamagnetic nanoparticles of high anisotropy respond strong to sub- GHz field beyond the regime of linear response up to room temperature. • Nanoparticle diameter (thus, strength of dipolar interactions) is crucial for stabilizing the high-frequency magnetic response at elevated temperatures. • At critically-high nanoparticle diameter, magnetic loss of power rapidly increase. [ABSTRACT FROM AUTHOR]

[Display omitted] • Discusses attributes that make iron-based adsorbents suitable for U(VI) adsorption. • Categorization of adsorbents into inorganic, organic, MOF, and carbon-based types. • Deep discussion of physicochemical characteristics and U(VI) adsorption mechanism. • Focuses on the conditions required for advancing research in U(VI) adsorption. Energy and environmental concerns have historically had an impact on the growth of civilization. In the last several decades, nuclear power has advanced rapidly since clean energy has proven to be convenient for storage. However, with an upsurge in nuclear power plants and the by-products they produce, noxious radioactive elements like uranium, which are harmful chemically and radiologically, have posed an imminent threat to aquatic and terrestrial life. Numerous approaches have been developed to deal with the shortcomings to maneuver these adversities. Among them, adsorption has been acknowledged as a simple, successful, and economically viable innovation that has received significant attention in recent years despite several limitations in terms of practical uses. In light of considerable investigations by several research organizations, medicine, catalysts, magnetic resonance imaging, and wastewater remediation represent merely some of the disciplines where iron-based adsorbents have garnered enormous curiosity. The application of these adsorbents to mitigate environmental pollutants has been steadily growing due to their superparamagnetism, low manufacturing expense, simplicity in modification, and biocompatibility. With the intent to objectively assess the potential for uranium removal in an ecologically safe manner, this review comprehensively explores various iron-based adsorbents (Fe-NAs), including inorganic, organic, metal–organic framework, and carbon-based materials. Furthermore, the article thoroughly investigates the synthesis processes and ways to enhance the surfaces of these adsorbents as well as delving into their fascinating physicochemical characteristics and adsorption mechanism. Finally, research prerequisites and prospective applications for future advancement have been highlighted. This review aims to furnish information that not only serves as a valuable reference but also ignites the spark of knowledge for researchers and professionals dedicated to this field. [ABSTRACT FROM AUTHOR]

The magnetic and electrical properties of two different sets of carbon nanospheres synthesised by chemical vapour deposition were investigated, using a state-of-the-art Physical Property Measurement System (PPMS). Scanning electron microscopy imaging of the carbon nanospheres revealed a difference in size with a diameters distribution of approximately 200–400 nm and 400–500 nm. PPMS magnetic measurements of the 400–500 nm diameter carbon nanospheres exhibited diamagnetism at high temperatures and clear superparamagnetic behaviour at very low temperatures (< 10 K). However, ferromagnetism was observed in carbon nanospheres of diameter < 400 nm. The results obtained from both inductively Coupled Plasma Mass Spectrometry and Mössbauer spectroscopy, and as well as the calculated saturation magnetisation indicate that the observed ferromagnetism in the carbon nanospheres of diameter < 400 nm is intrinsic and could not be accounted for by the magnetic impurities such as Fe and Ni introduced during the synthesis process. The electrical properties of a network of carbon nanospheres were investigated and showed a variable range hopping class of conductivity. [Display omitted] • Carbon nanospheres synthesised by chemical vapour deposition for 20 min exhibits ferromagnetic behaviour. • The ferromagnetism is intrinsic and cannot be accounted for by magnetic impurities. • Super-paramagnetic characteristic is depicted at 2 K in carbon nanospheres synthesised for 40 min. • The electrical resistance shows a variable range hopping class of conduction at low temperatures and thermal activation conduction at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, we studied the dynamics of the graphitization in diamond induced by high repetition rate fs laser. Unlike the dynamics in the case of employing low repetition rate fs laser, the graphitized region can grow both toward and along the laser beam. For surface processing, the experimental results have revealed that employing multi-scanning can effectively reduce the fluctuations of the thicknesses of the graphitization wire, but it is useless for fabricating a continuous graphitization wire inside diamond. There emerges a comb structure, which consists of an array of graphitization filaments. The growth of each filament in the comb structure can be classified by four growth regions, based on which we discussed the dynamics of the formation of this comb structure. Furthermore, we measured the magnetic properties of both surface-irradiated and inside-irradiated samples. The surface graphitized sample shows a common diamagnetism, but the internal graphitized sample exhibits an unusual superparamagnetism. • Dynamics of graphitization process is more complicated at high repetition fs laser. • Multiple scanning improves uniformity of graphitization wires on diamond surface. • The comb structure always emerges when laser repetition more than 100 kHz. • The formation of the comb structure is discussed based on filament growth dynamics. • The internal graphitized sample shows a rare superparamagnetism. [ABSTRACT FROM AUTHOR]

Mn x Zn 1-x Fe 2 O 4 (x = 0–1) solid solution was prepared using the TREG-mediated solvothermal method. 10–12 nm spherical superparamagnetic particles (except for ZnFe 2 O 4) were obtained. At room temperature, the ferrites have lower magnetic saturation (Ms) than magnetite. However, at 10 K, it is precisely the opposite. DRX and EXAFS showed that incorporating Zn2+ ions in tetrahedral A-sites provokes a redistribution of Mn and Fe ions in octahedral B-sites of the mixed spinel structure. For Zn concentrations from x = 0.5 and below, the Mn and Fe ions are almost equally distributed between A and B-sites. Therefore, at low Zn concentrations, the small migration of Fe and Mn ions to B-sites increases the magnetic moment of B sub-lattices and, consequently, the total magnetic saturation. In addition, Mn2+ oxidized to Mn3+ and, simultaneously, Fe3+ reduced to Fe2+, affecting the magnetic properties. The increment of Zn concentration severely reduces the magnetization. [ABSTRACT FROM AUTHOR]

• Ti2MnAl crystallizes with significant atomic disorder resulting in random mixing of constituent elements. • Atomic disorder plays an important role in determination of physical properties. • Ti2MnAl exhibits Pauli's paramagnetic behaviour. • Non-interacting superparamagnetic clusters emerge at low temperatures due to defects. • Disorder give rise to a negative temperature coefficient of resistivity. Search for novel spintronic materials in family of Heusler alloys has attained significant interest in recent years. In this context, Ti 2 MnAl is interesting as it is predicted to host spin gapless semiconducting state and compensated ferrimagnetic ordering. Here we report a detailed experimental investigation of Ti 2 MnAl. Our studies reveal that Ti 2 MnAl crystallizes in cubic structure with strong atomic disorder along with Pauli paramagnetic behaviour. The influence of disorder manifests in form of non-interacting superparamagnetic clusters at low temperatures and negative temperature co-efficient of resistivity. The carrier concentration obtained from Hall resistivity rules out the possibility of spin gapless semiconducting state. Our studies indicate that atomic disorder plays an important role in determination of physical properties of Ti 2 MnAl. [ABSTRACT FROM AUTHOR]

The applicability, peculiarities, and progress of the high resolution 1H, 13C, and 15N NMR spectroscopy for elucidating the spin crossover phenomenon were shown. NMR is quite possible to study such systems, extracting a lot of useful information about the properties of complexes in solution. The use of NMR spectroscopy makes it possible to estimate the structural and dynamic peculiarities of complexes possessing a spin crossover. [Display omitted] The applicability, peculiarities, and progress of the high resolution 1H, 13C, and 15N NMR spectroscopy for elucidating the spin crossover phenomenon were shown. The results obtained by the NMR method are compared with the results found by other physicochemical methods. Though, the coordination environment in a solution can change significantly compared with a solid state. As a result, the magnetic properties of the complex as a whole can also vary significantly. NMR is quite possible to study such systems, extracting a lot of useful information about the properties of complexes in solution. The use of NMR spectroscopy makes it possible to estimate the structural and dynamic peculiarities of complexes possessing a spin crossover. In addition, the presence of a "magnetic response" to changing external conditions provides opportunities for targeted design of NMR sensor systems. [ABSTRACT FROM AUTHOR]

The intrinsic switching field defined as the minimum field to induce spontaneous magnetic reversal is calculated at finite temperatures for a uniaxially anisotropic single domain particle using a formalism based on the generalized free energy function of the system. For a fine ferromagnetic particle coupled to a constant temperature heat bath, the switching field is smaller than the field predicted by the Stoner-Wohlfarth (SW) theory and the difference is dependent on the direction of the applied field resulting in breaking of the symmetry of the SW astroid. • Broken symmetry of Stoner Wohlfarth astroid at finite temperatures. • Significant thermal reduction of switching field if the applied field is axial. • Temperature invariance of prefactor of Arrhenius law involving free energy barrier. [ABSTRACT FROM AUTHOR]

Iron-gallium borate, Fe x Ga 1− x BO 3 , single crystals have been synthesized by the solution in the melt technique. The exact x -values in the crystals have been determined by X-ray fluorescence analysis and checked by Energy Dispersive X-Ray Spectroscopy. Scanning Electron Microscopy has been used to map distributions of iron and gallium ions in the crystals. The electron magnetic resonance (EMR) spectra as well as field and temperature dependences of the magnetization obtained by SQUID reveal the existence of different magnetic phases in different x ranges, viz. weakly ferromagnetic antiferromagnetic, magnetic cluster and paramagnetic phase. For crystals with 0.32 ≤ x ≤ 0.83, the Néel temperatures, T N , have been determined. The magnetometry of these crystals suggests the existence of another magnetic transition at a temperature well below T N , tentatively ascribed to a Morin type transition. Detailed EMR and SQUID studies of the crystal with x ≈ 0.2 reveal the existence of magnetic nanoclusters showing superparamagnetic behaviour. Using a laboratory developed code based on the Monte-Carlo technique, spatial distributions of dia- and paramagnetic ions in the crystal with x ≈ 0.2 has been visualized and possible cluster sizes have been estimated. • Fe x Ga 1− x BO 3 can be weakly ferro- antiferromagnetic, superpara- or paramagnetic. • Superparamagnetism in magnetically diluted crystals arises from magnetic clusters. • Fe x Ga 1− x BO 3 are promising as fine-tunable materials for advanced applications. [ABSTRACT FROM AUTHOR]

MgNi ferrite nanoparticles were prepared successfully via wet sol-gel route using the nitrates of proposed elements i.e. Mg, Ni and iron were used as precursors with citric acid as fuel. The prepared materials were annealed at a temperature of 900∘C to achieve the best properties. To know structural, morphological, elastic and magnetic properties, the synthesized nanoparticles were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscope (HRTEM), vibrating sample magnetometer (VSM), FTIR spectroscopy and Raman spectroscopy. The results of XRD, FTIR and Raman spectroscopy patterns are indicative of formation of ferrite nanoparticles and the structural studies confirm the inverse-spinel structure with crystallite size 35–61 nm. The formation of spinel ferrite structure is confirmed by absorption bands corresponds to vibration of tetrahedral site-A and by absorption bands corresponds to the octahedral site-B. Crystallite size calculations were carried out using WilliamFson-Hall plot. Rietveld refinement was applied to assure the crystal structure and allied parameters. The magnetic analysis of the prepared samples was carried out by VSM indicates that the nanoparticles exhibited superparamagnetic behavior having high magnetic saturation (M S) and negligible coercivity (H C). The elastic and magnetic properties through absorption bands found degraded at higher magnesium compositions. [Display omitted] • High-Magnesium MgNi ferrite nanoparticles posses elastic stability. • Traces of alpha hematite phase detected in high-magnesium composition. • Magnetic field strength increased. • MgNi ferrites exhibit ferromagnetic characteristics. [ABSTRACT FROM AUTHOR]

• A series of Mn 2 -, Mn 3 -, Mn 4 -, and Mn 6 -based manganese carbonyl chalcogenide (Se, Te) cluster anions were synthesized via one-pot reactions of chalcogen powders and Mn 2 (CO) 10 with the absence or presence of metathesis salts in basic solutions. • These E −Mn−CO (E = Se, Te) clusters could undergo structural transformation, dioxygen activation, se radical coupling, alkylene bromide functionalization, hydride removal/addition, or oxidative carbonylation to produce a series of functionalized or oxidative products. • The Mn 3 -, Mn 4 -, and Mn 6 -based selenides or tellurides were found to have paramagnetic properties with S = 1 or S = 1 + 1/2 for the se radical-containing Mn 3 cluster. • The rare manganese chalcogenide cluster anions revealed low-energy-gap semiconducting characteristics, which were well-elucidated with DFT calculations. The chemistry of manganese−chalcogenide clusters has attracted extensive attention due to their versatile syntheses, unique structures, and potential applications in magnetic and semiconducting materials. In this short account, we will review our recent progress in the chemistry of Mn 2 -, Mn 3 -, Mn 4 -, and Mn 6 -based manganese carbonyl chalcogenide (Se, Te) cluster anions, in which their facile one-pot syntheses, reversible structural transformations, and unique chemical and physical properties were described. These E −Mn−CO (E = Se, Te) cluster anions were found to react with O 2 , alkylene bromides, strong acids, or even CO, giving various oxidative or functionalized Mn 3 -, Mn 4 -, and Mn 6 -based paramagnetic tellurides or selenides derivatives. These manganese carbonyl selenides or tellurides exhibited semiconducting behaviors with tunable energy gaps and moderate electrical conductivities. Their efficient electron communication was mainly attributed to the weak interactions between cluster anions and cations, which were further investigated with DFT calculations. This mini-review showcases our recent progress on the chemistry of selenium- or tellurium-containing manganese carbonyl cluster anions regarding their syntheses, structures, and reactivities. Their intriguing O 2 /Se 8 activation, Se radical coupling, alkylene bromide functionalization, hydride removal/addition, and oxidative carbonylation were demonstrated. Their unexpected paramagnetism and semiconductivities were also illustrated. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferritin is an important biological system and found in blood of living organisms. Inorganic cores of this material are 8 nm in size. The cores are surrounded by protein shells which reduce interparticle interaction. Particle size distribution present in ferritin is determined from transmission electron micrograph. This distribution can be described by a log normal distribution function. The magnetic field (0–70 kG) dependence of the magnetization at different temperatures are analyzed considering the estimated particle size distribution. The resulting mean particle magnetic moment is temperature independent and equal to 310 μ B. Saturation magnetization and antiferromagnetic susceptibility of ferritin decrease with increasing temperature. • Ferritin contains an antiferromagnetic inorganic core surrounded by a protein shell. • Langevin function assumes that all particles have same magnetic moment. • Particle size distribution present in a sample of ferritin is determined from transmission electron micrograph. • Magnetization data on ferritin in superparamagnetic region are analyzed considering a distribution in particle size. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cd x Co 1− x Fe 2 O 4 (0 ≤ x ≤ 07) nanoferrites were synthesized by glycol-thermal process. • XRD and FTIR confirmed single phase spinel structure. • Mossbauer spectroscopy revealed transformation in magnetic phases due to addiction Cd2+ ions. • Improvement in magnetic properties Cd x Co 1- x Fe 2 O 4 oxides. The Cd2+ substituted Co 1- x Fe 2 O 4 with concentrations of (0 ≤ x ≤ 0.7) nano ferrites were synthesized using the glycol-thermal method. X-ray diffraction (XRD) and Fourier-transformed infrared (FT-IR) spectroscopy confirmed the structural formation and nanocrystalline structure of spinel ferrites. Samples possess a cubic spinel lattice structure with crystallite sizes varying between 5.1 nm and 15.5 nm. Transmission electron microscopy (TEM) revealed fine particles which are nearly spherical in shape. The 57Fe Mössbauer spectral studies showed an ordered magnetic spin state for x ≤ 0.5 which transforms to a paramagnetic phase for x ≥ 0.6 due to the weakening of super-exchange interactions. The saturation magnetization (M S) was the highest at x = 0 with a value of 73.3 emu/g and fluctuated between 44.3 emu/g and 19.8 emu/g after the addition of non-magnetic Cd2+ ions. The field dependence of dM / dH curves reveals the finite size effect which leads to the frustration in magnetic moments. [ABSTRACT FROM AUTHOR]

The effect of thermobaric treatment (TBT) at Р = 5.5 GPa T = 1900 °C for 4 h on the concentration of single substitutional atoms (P1 centers) in nitrogen-doped synthetic single crystal Ib type diamonds grown by the temperature gradient high-pressure high-temperature (TG-HPHT) method and on their magnetic properties in the temperature range of 2–300 K was investigated. The initial concentration of P1 centers in 2 crystals was 3.0 × 1019 cm−3 and 5.6 × 1019 cm−3, respectively, which decreased by ~96–98 % after TBT. At T < 10 K, an anomalous hysteresis of the magnetic moment is observed in the range of magnetic fields up to H c = 70 kOe, the amplitude of which is half the value of the paramagnetic saturation moment, corresponding to the number of spins of the P1 centers. The shape of the hysteresis loops after subtracting an intrinsic diamond diamagnetic component and the calculated paramagnetic component indicates a granular (local) superconducting state. The fact that the amplitude of the magnetic moment generated by superconducting currents is equal to half the total number of Bohr magnetons of P1 centers may indicate that elementary currents occur in pairs of adjacent P1 centers. As a result of a decrease in the number of P1 centers in diamonds after TBT, the saturation values of the paramagnetic moment and the amplitude of the diamagnetic moment of the induced superconducting currents decrease proportionally. [Display omitted] • SC component of magnetization at T < 15 K presents in N-doped HPHT diamonds after TBT. • Granular superconductivity magnetization reaches half the paramagnetic component. • Pairs of nitrogen P1 centers create superconducting nanocircuits in diamond. [ABSTRACT FROM AUTHOR]

[Display omitted] Detonation nanodiamonds with a particle size of 5 nm and a carboxylated surface are easily modified by doubly charged copper ions to form copper chelate complexes. The concentration of copper complexes in a dry powder of such nanodiamonds is well monitored by the method of electron paramagnetic resonance, both by the signal width of intrinsic paramagnetic centers in nanodiamonds and by the signal shape for the surface Cu2+ ions themselves, including the set of hyperfine splitting lines for the parallel component and the line with an unresolved hyperfine structure for the perpendicular component. [ABSTRACT FROM AUTHOR]

A high degree of spin polarization in half-metallic double perovskites is a prerequisite for several applications in spintronics, which depends crucially on the cationic order of the systems. This paper reports a study on tailoring the structure and morphology of nano-sized Sr 2 Fe 1- x Zn x MoO 6 (x = 0.05, 0.1, 0.15) materials to improve their spin polarization. The combined analysis of synchrotron X-ray diffraction and magnetization data shows that Zn replaces Fe in the B sites. Although the majority of particles have lateral dimensions in the range 30–60 nm as observed by scanning electron microscope, the samples with x = 0.1 and 0.15 show finite-size effects with superparamagnetism below room temperature and a reduced Curie temperature (from 410 K for x = 0.05–390 K for x = 0.15). The results are due to the formation of networks of insulating Mo–O–Zn–O–Mo linkages and anti-phase boundaries, which divide the particles into smaller domains with a mean diameter of ∼11 nm as determined via a Langevin fit. The almost perfectly ordered structure in the nanodomains is responsible for a high magnetoresistance ratio. A value of -42% at 5 K in 50 kOe is recorded for the sample x = 0.15. Via fitting the magnetoresistance curve using the Inoue-Mekagawa theory, the spin polarization of 99% is determined. [ABSTRACT FROM AUTHOR]

Novel rare-earth-contained W-based in-plane chemically ordered (W 2/3 R 1/3) 2 AlC (R = Gd, Tb, Dy, Ho, Er, Tm and Lu) i -MAX phases have been firstly reported. All are identified to be C 2/ c monoclinic by structural analysis. Magnetic ground state is found to change from linear antiferromagnetism for R = Gd to paramagnetism for R = Lu with gradually decreased ordering temperature with the evolution on magnetic configurations. By exfoliation and delamination, brittle W 1. 33 C MXene fragments have been obtained and demonstrated undesired specific capacitance of 76 F g−1 at 1 A g−1. By making W 1. 33 C/Ti 3 C 2 composite MXene, flexible free-standing paper has been obtained and the specific capacitance is substantially enhanced to 183 F g−1 with good retention, which is the highest performance realized in W 1. 33 C MXene up to now. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAp) is one of the most studied biomaterials for orthopaedic applications, yet its commercialization holds in a few of the lags, such as non-antibacterial activity and target deficiency. In this context, we aimed to design a biphasic nanoassembly of Ferric-HAp-Zincite (ZFHAp) via a one-step co-precipitation method. Ferric-HAp obtained Ca 9·333 Fe 1·167 (PO 4) 7 phase in all the samples, and the secondary phases such as Ca 9 Fe(PO 4) 7 and Ca 28·8 Fe 3·2 (PO 4) 21 O 0.5 were governed by the Fe dopant concentration. Along with ferric-HAp, zincite phases were present in all the samples depending on the concentration of Zn precursor. The synthesized ZFHAp samples were hexagonal in structure with size <100 nm, and a dual morphology, i.e., rod-shaped (77.8 ± 10 nm; major corresponding to HAp) and particulate shaped (30.9 ± 5 nm; minor due to Zincite). Doping of iron imparted paramagnetism resulting in the magnetic target efficiency. ZFHAp samples showed excellent self-antibacterial activity against clinically significant two Gram-positive (E. hirae, S. aureus) and two Gram-negative (E. coli, S. paratyphi) bacteria with lower MIC values (60–80 μg/ml). The antibacterial mechanism was found to be ROS independent and due to the linear release of Zn2+ and Fe3+ ions. The designed ZFHAp samples showed no cytotoxicity up to 5 mg/mL and exhibited 3 times higher bone cell proliferation along with the significant Alkaline Phosphatase (ALP) activity. The prepared nanomaterials also did not show any inflammatory response to bone cells. These findings entitle ZFHAp as a potential candidate for orthopaedic as well as other biomedical applications subject to further clinical trials. [ABSTRACT FROM AUTHOR]

Despite being difficult to identify, extremely dilute oxygen vacancies have been widely reported to play an important role in enhancing magnetism in ZnFe 2 O 4. The mechanisms underlying this enhanced magnetism have not been well understood for a long time and remain controversial because the formation of oxygen vacancy-rich ZnFe 2 O 4 can be accompanied by changes in the chemical/physical characteristics, especially the composition, particle size, surface morphology and cation distribution, which can significantly affect the magnetization. An open and important question is whether and to what extent the enhanced magnetization can be attributed only to oxygen vacancies. In this study, the relationship between the magnetization and oxygen vacancies in ZnFe 2 O 4 was definitively determined by using a carefully designed "shake-and-heat" treatment to prepare vacancy-rich samples while keeping the other crystal/surface parameters constant. Compared to the nearly vacancy-free paramagnetism samples, the vacancy-rich samples exhibited a higher magnetization of approximately 5 emu/g at both 300 K and 2 K. The Fe3+-O2--Fe3+ superexchange paths broken by oxygen vacancies then resulting in the Fe3+-Fe3+ ferromagnetism configuration. Meanwhile, the oxygen vacancy is highly diluted then the ferromagnetism configuration is confined in a single super-cell, favoring a short-range magnetic ordering at room temperature. The concentration of oxygen vacancies was calculated to be 0.68% by magnetization measurement. Our results may shed a light on how oxygen vacancies affect magnetism. [ABSTRACT FROM AUTHOR]

Bi 25 FeO 39 microcrystals were synthesized via a one-pot hydrothermal process without additives, where their hierarchical structures could be designed from tetrahedron to orchid and marigold by the increment of pH values and reaction time. For all types of as-prepared Bi 25 FeO 39 , a high crystallinity and purity was confirmed in XRD and XPS analysis. A good thermal stability up to 1000 °C was revealed by DSC-TG with two endothermal peaks corresponding to decompositing and melting. A magnetic transition between ferromagnetism and paramagnetism around 36.3 K was distinguished from thermomagnetic curves as well as hysteresis loops at 5 K and 300 K respectively. In contrast to tetrahedron and orchid shaped Bi 25 FeO 39 , marigold shaped Bi 25 FeO 39 exhibited a higher magnetization up to 4.8 emu/g at 5 K and enhanced photocurrent density around 0.37 μA/cm2. The special crystal arrays and increased concentration of Fe should be responsible for it. This work paves an attractive way for facile preparation and potential applications of sillenite materials. [ABSTRACT FROM AUTHOR]

Pure semi-ionic F-doped graphene with the s-F concentration high up to 17.4 at.% (s-FG-17.4) and covalent F-doped graphene with the c-F concentration of 17.8 at.% (c-FG-17.8) were synthesized by fluorination of graphene respectively at the low temperature of 100 °C and the conventional temperature of 200 °C. The electronic and magnetic properties of the two samples were studied. The results show that s-FG-17.4 is metal and exhibits strong ferromagnetism with the Curie temperature of 229 K and high magnetization of 1.1 emu/g; by contrast, c-FG-17.8 is semiconductor and exhibits spin-half paramagnetism with low magnetization of 0.1 emu/g. Thus, this study provided a reliable method to synthesize high-concentration pure s-FG and proposed an effective sp 3 dopants for obtaining metallic and ferromagnetic graphene with high magnetization. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, the suitability and potential of two biocompatible mixed valent non-stoichiometric spinel nanoferrites viz., Zn 0.5 Ca 0.5 Fe 2 O 4 (ZCNF) and Mg 0.5 Ca 0.5 Fe 2 O 4 (MCNF) with a minor impurity of CaCO 3 have been explored for magnetic hyperthermia and in-vitro cytotoxicity against normal and lung cancer cell lines. Nanocrystalline samples of ZCNF and MCNF in fcc structure were synthesized using the citrate-based sol-gel method and characterized by a variety of standard techniques. 57Fe Mössbauer spectroscopy, electron spin resonance and dc-magnetometry studies revealed that ZCNF is dominantly superparamagnetic while, MCNF is a soft ferrimagnet at 300 K. The maximum specific absorption rate (SAR) for 1 mg/mL suspension of nanoferrite powder in de-ionized water was found to be 179 W/g and 338 W/g for ZCNF and MCNF, respectively. Further, the highest hyperthermia temperature of 41.5 °C and 52 °C was achieved in 900 s at 15.98 kA/m for ZCNF and MCNF, respectively. Both ZCNF and MCNF showed good cytocompatibility with a tested concentration of 0.5 mg/mL against the human embryonic kidney HEK-293 (>75% cell viability) cell line. Additionally, simulated in-vitro treatment at an optimum magnetic hyperthermia temperature of 45 °C for 30 min in the presence of ZCNF and MCNF powder (up to a concentration of 1 mg/mL) led to suppression of ∼55% lung cancer cell lines (A549) while, in similar simulated condition the cell viability of normal HEK 293 cell lines remain unaffected. In summary, ZCNF and MCNF are appropriate therapeutic nanomaterials for magnetic hyperthermia-related cancer therapies. [Display omitted] • Synthesis of non-stoichiometric Zn 0.5 Ca 0.5 Fe 2 O 4 (ZCNF) and Mg 0.5 Ca 0.5 Fe 2 O 4 (MCNF) nanoferrites by sol-gel route. • SAR = 179 W/g and 338 W/g with decent ILP values of ∼ 2.1 and 3.9nHm2kg−1 for ZCNF and MCNF respectively. • ZCNF and MCNF showed good cytocompatibility with a tested concentration of 0.5 mg/mL on embryonic kidney HEK-293 cells. • Lung cancer A549 cells incubated in the presence of ZCNF and MCNF at 45 °C (simulated hyperthermia conditions) for 30 min led to reduction in cell viability upto 55%. • ZCNF and MCNF are suitable nanomaterials for magnetic hyperthermia based cancer theranostics. [ABSTRACT FROM AUTHOR]

The present comparative study explores the effect of magnetic (Mn) and non-magnetic (In) doping on structural, magnetic, and quantum-transport properties of Bi 2 Se 3 topological insulator. Un-doped as well as Mn, In-doped Bi 2 Se 3 samples have been synthesized using the solid-state reaction method, confirmed by HR-TEM results. The XRD pattern along with Rietveld refinement reveals that, both Mn and In-dopants substitute the Bi-ion together with slightly interstitially incorporation in host Bi 2 Se 3. It is also found that In-doping is more preferable for Bi-substitution than Mn, which is well supported through our XPS analysis. The study of magnetism indicates the diamagnetic nature of un-doped Bi 2 Se 3 gradually transformed into ferromagnetism for high Mn-doping, whereas In-doped Bi 2 Se 3 shows a mixing of diamagnetism and paramagnetism. Electrical-transport establishes that In-doped Bi 2 Se 3 preserves the hostʼs metallic nature; however, the arrest of metallic response is observed through the evidence of Kondo effect below 185 K for high Mn-doping. Interestingly, the Mn-doping creates a transformation of hostʼs weak anti-localization (WAL) towards weak localization (WL), and produces a significant reduction in the phase coherence length (l φ) of host Bi 2 Se 3 , verified by the magneto-conductance analysis. Whereas, In-doping shows relatively minor deviation in hostʼs WAL effect for higher doping limit. • Un-doped and Mn, In-doped Bi 2 Se 3 are synthesized using a solid-state reaction method, confirmed by HR-TEM results. • The structural analysis justifies that, In-doping is more preferable for Bi-substitution than Mn in host Bi 2 Se 3. • Magnetism study indicates Mn-doping transforms the hostʼs DM into FM, whereas In-doping shows a mixing of DM and PM. • In-doping preserves the hostʼs metallic nature, which is arrested for high Mn-doping through the evidence of Kondo effect. • In-doping slightly deviates the hostʼs weak anti-localization, which transforms towards weak localization for Mn-doping. [ABSTRACT FROM AUTHOR]

• Novel six tetracoordinate Co(II) complexes. • Molecular spectroscopy of products. • New structural information. • Deep magnetochemical investigation and revelation of axial ZFS parameters D. • Ab initio calculations. A series of tetracoordinate mononuclear Co(II) complexes [Co(L1) 2 (X) 2 ] (1 - 3) and [Co(L2) 2 (X) 2 ] (4 - 6) {where L1 = 2-amino-1-methyl-benzimidazole; L2 = 4-methylquinoline; X = Cl, Br, I} have been synthesized and studied in detail. Compounds were characterized by spectroscopic methods along with their molecule structure determined by the single-crystal X-ray diffraction. All complexes have been investigated in the static magnetic field B dc = 0.1 T using SQUID magnetometry. DC magnetic data were fitted by a spin Hamiltonian model appropriate to a zero-field splitting system. The axial zero-field splitting parameters D ranged as -14.44 (1), -13.05 (2), -7.50 (3), -6.76 (4), +7.19 (5), -5.58 (6) cm−1. The experimental zero-field splitting parameters are compared with those obtained by ab initio calculations of the CASSCF + NEVPT2 + SOC quality. [Display omitted] [ABSTRACT FROM AUTHOR]

Both theoretical calculations and experiments indicate that a monolayer CoSb/SrTiO 3 film has high-temperature superconductivity resembling the case of FeSe/SrTiO 3. However, no superconductivity was found in the bulk CoSb, even under high pressure. Moreover, the magnetic properties of CoSb have always been controversial. Here, we have studied the electrical property, magnetic property, and X-ray photoelectron spectroscopy (XPS) of CoSb single crystals. Electrical and magnetic transportation measurements reveal that CoSb is a Pauli paramagnetic metal with non-Fermi liquid behavior. The XPS results showed that both Co and Sb in CoSb are in the zero-valence state, and they form an alloy in which the metallic bond is dominant. The Pauli paramagnetism of CoSb originates from its itinerant electrons. Therefore, unveiling the electronic states of CoSb single crystal not only help us understand its magnetic properties, but would also pave the way for searching for the possible high-temperature superconductivity. • CoSb single crystals with large size were synthesized. • CoSb is a Pauli paramagnetic metal with non-Fermi liquid behavior. • XPS analysis indicates that both Co and Sb are in the zero-valence state in CoSb. • The Pauli paramagnetism of CoSb originates from its high-density itinerant electrons. [ABSTRACT FROM AUTHOR]

• Using the coprecipitation method, Ce doped Mg-Ni ferrite nanoparticles were successfully synthesized. • The crystallite size of the synthesized samples lies in the range from 6 nm to 12 nm. • Superparamagnetic nature of the samples makes them a potential material for preparation of ferrofluid. • As Ce3+ ion concentration increases, dielectric constant and loss tangent decreases making them a potential material for microwave-based applications. In this work the effect of Ce3+ ion doping on microstructure, crystallite size, magnetic, optical and dielectric characteristics of Mg 0.5 Ni 0.5 Fe 2-x Ce x O 4 (0 ≤ x ≤ 0.1) ferrite nanoparticles are discussed which are synthesized by using the co-precipitation method. The X-ray diffraction analysis confirms the cubic phase of all the synthesized samples and further confirmation of ferrite structure is supported by Fourier transformed infrared spectroscopy characteristic peaks. The crystallite size was determined in the range of 6 nm to 12 nm with increasing lattice parameter value from 8.347 Å to 8.359 Å on increasing Ce3+ ion doping. High-resolution transmission electron microscopy analysis confirms the spherical shape of the nanoparticles with agglomeration. Magnetic hysteresis curves analysis reveals that saturation magnetization of the Mg-Ni ferrite nanoparticles decreases with increasing Ce3+ ion concentration. Vibrating sample magnetometer analysis confirms the superparamagnetic nature of the synthesized samples. Electron spin resonance spectroscopy confirmed the reduction in g-value and spin relaxation time with increasing Ce3+ ions doping. The band gap increases from 1.79 eV to 2.59 eV with increasing Ce3+ ion doping. The magnetic properties of the synthesized samples make these nanoparticles a potential candidate for the synthesis of ferrofluids and biomedical application. Dielectric study confirms the decrease in dielectric constant (ε′) and loss tangent (tan δ) against increasing frequency with increasing Ce3+ ion concentration making the nanoparticles a potential candidate for the high frequency applications. [ABSTRACT FROM AUTHOR]

Diamond, silicon and germanium are widely used technological materials, whose electron structures are tabulated and understood very well. Yet the detailed picture of various diamagnetic contributions and their interplay with the paramagnetic effect, especially at the ab initio level, due to the complexity of this problem remains largely unknown. In our study, based on the ab initio electron band structure approach, all possible magnetic contributions, including the Langevin (Larmor) diamagnetism and the Van Vleck paramagnetism accounted in the second order of the perturbation treatment, are analyzed quantitatively. The Van Vleck contribution has been adapted to the band structure calculations by performing integration over k -points. Also, the partial diamagnetic contributions of core and valence electrons are obtained and discussed in detail. Of all terms there is only one — the Langevin diamagnetism of the valence electrons, which is not well defined quantitatively due to the contribution from the interstitial region. We discuss possible approaches to partitioning this contribution among neighboring crystal sites, based on the Bader charge separation and introducing the area of depleted electron density, excluded from the integration. Under various assumptions for the interstitial region, we have found that the magnetic susceptibilities for diamond, silicon and germanium lie in the range -13.4/-9.3, -4.7/-4.0 and -8.4/-8.8 (volume values, in units of 1 0 − 7 ), correspondingly. In general, this is consistent with the available experimental values, albeit the numerical uncertainty typically reaches tens of percent. • ab initio (DFT) calculations of magnetic susceptibilities for diamond, silicon and germanium. • all magnetic contributions (Langevin, Van Vleck, core, valence) are analyzed quantitatively. • partitioning Langevin valence contribution among neighboring crystal sites, Bader separation. • Van Vleck contribution is adapted to band structure calculations integrating over k-points. [ABSTRACT FROM AUTHOR]

Superparamagnetic magnetite (Fe 3 O 4) has potential biomedical applications, but its synthesis can be challenging and costly. We present a simple and facile method for synthesizing superparamagnetic magnetite via the co-precipitation method. The pH and stabilizer concentration were optimized to obtain high purity Fe 3 O 4 nanoparticles with superparamagnetic characteristics, despite having an aggregated morphology. The results showed that the synthesized particles were micrometer-sized, and exhibited superparamagnetic behavior with a value of 40 emu/g. The conventional wisdom on superparamagnetic behavior is to attribute the phenomenon to the presence of nanosized crystallites and nanoparticles in the aggregated structure, however, our computational analysis through density functional theory shows that strain-related effects are an underlying cause for the paramagnetism of magnetite as well, which explains our experimental observations. Overall, the co-precipitation method presented in this study offers an easy, non-toxic, and fast method for synthesizing Fe 3 O 4 nanoparticles, which is suitable for industrial-scale production. [Display omitted] • Fe 3 O 4 particles were micron-sized, exhibiting superparamagnetic behavior of 40 emu/g. • Strain-related effects are an underlying cause for the paramagnetism of Fe 3 O 4 powders. • Tetrahedral Fe vacancy formation is favored in nanosize range. • The spin channels are fully symmetric on DOS patterns of strained Fe 3 O 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • Annealing effect implied oxidation of magnetite and enhanced the crystallinity of mixed nickel-copper and nickel-zinc ferrites; • Morphology observation exhibited agglomerated particles showing irregular shapes, and having homogeneous chemical composition; • 57Fe Mössbauer spectra revealed the superparamgnetic relaxation behaviour for magnetite and nickel-zinc ferrites; • Nickel-copper ferrites Mössbauer spectrum has reflected the ferrimagnetic nature. • Nickel-zinc ferrites show interesting magnetic properties making them a candidate for hyperthermia application. This work aims to investigate the magnetite obtained by coprecipitation, as well as the mixed ferrites of nickel-copper and nickel-zinc. The as-prepared samples were then annealed at a temperature (T an) of 1000 °C. The as-prepared magnetite shows a polycrystalline spinel structure having an average of crystallite size (D XRD) of 8 nm, while other as-prepared mixed ferrites are structurally amorphous. Annealing at T an has resulted in an improvement in the crystallinity of both nickel-copper ferrites (NCF, D XRD = 92 nm) and nickel-zinc ferrites (NZF, D XRD = 83 nm), both of which exhibit a cubic spinel structure. The thermal treatment in air atmosphere has also led to the oxidation of magnetite into hematite. Morphological observations suggest that the magnetite nanoparticles are nearly spherical, whereas the NCF and NZF particles indicate irregular shapes, which tend to aggregate. Magnetic curves reveal that the NCF exhibits a blocking temperature (T B) close to room temperature, while the NZF sample displays the lowest T B at 45 K. Additionally, the NZF exhibits a higher M s value of 80.4 emu/g and displays a narrow hysteresis loop, which makes it suitable for applications in hyperthermia. The 57Fe Mössbauer study on magnetite and NZF indicates broadening spectra, which is due to superparamagnetic relaxation, thus the fit their spectra was established with hyperfine field distribution component. Regarding the NCF Mössbauer spectrum was adjusted by superimposing two sextets reflecting the presence of Fe3+ at the A and B sites of spinel. The hyperfine parameters, including the isomer shift, and hyperfine field, have been systematically reported in the present study. [ABSTRACT FROM AUTHOR]

Six lines ferrihydrite nanoparticles are synthesized following a chemical route. The sample is characterized using x-ray diffractometry, Fourier transform infrared spectroscopy, transmission electron microscopy and vibrating sample magnetometry. Average crystallite size is 5 nm. The sample exhibits superparamagnetic behavior. Magnetization versus magnetic field data in the superparamagnetic region are analyzed considering a distribution in particle size. Temperature dependence of saturation magnetization originating from surface spins and antiferromagnetic susceptibility of particle cores are studied. • Saturation magnetization decreases with increasing temperature. • Magnetization of antiferromagnetic particles is due to uncompensated surface spins. • Surface magnetization of crystals is expected to decrease linearly with temperature. • Temperature variation of saturation magnetization of six lines ferrihydrite is studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc ferrite nanoparticles are tailored by doping calcium and dysprosium at tetrahedral and octahedral sites respectively. • Enhanced UV absorption and low optical band gap suggests its usefulness for removing organic impurities from water. • Narrow hysteresis loops indicates the ferrimagnetic behavior. • Negligible retentivity and coercivity point to superparamagnetism of the grown ferrite compositions. • ·Magnetization, dielectric conductivity and dielectric loss predict its use as soft magnetic & microwave applications. This work is aimed to modify the properties of zinc ferrite (ZnFe 2 O 4) by introducing 5 %, 10 % and 15 % calcium (Ca) and dysprosium (Dy) each in host lattice. Accordingly Ca and Dy co – doped zinc ferrite nanoparticles with general formula Ca x Zn 1-x Dy x Fe 2-x O 4 (x = 0.0, 0.05, 0.10, 0.15) were synthesized by chemical co-precipitation technique using oleic acid as surfactant. The structure was found to be face centred cubic spinel with Fd3m space group as revealed by powder X -ray diffraction. The crystallite size determined in the range 26 – 17 nm decreases whereas lattice parameter increases with increase in 'x'. Morphological analysis by high resolution scanning electron microscopy shows decrease in agglomeration with increase in doping concentration. The presence of all essential elements was confirmed by energy dispersive X -ray spectra. The optical band gap which increases slightly from 1.84 eV for x = 0.0 to 2.10 eV for x = 0.15 suggests that materials could be good photo catalysts for removing organic contaminants from water. Electron paramagnetic resonance spectroscopy was employed to observe the paramagnetic response. Lande g – factor values determined in the range 2.00 – 2.014 confirms the presence of unpaired electrons in the system. Increase in peak to peak line width (H pp) from 342 G to 477 G for x = 0.0 to 0.15 respectively suggests decrease in super-exchange interactions. Narrow hysteresis loops obtained by vibrating sample magnetometer (VSM) depicts ferrimagnetic and soft magnetic behavior. Decrease in saturation magnetization (M S) with increase in 'x' is related to decrease in A – B type super-exchange interactions. Very small values of retentivity (M R) and coercivity (H C) suggests that prepared nanoparticles are super-paramagnetic. Increase in H C with increase in 'x' is attributed to increase in crystalline anisotropy. The behavior of frequency and temperature dependent dielectric constant as well as frequency dependent dielectric loss has been explained on the basis of Maxwell – Wagner model and Koop's theory. [ABSTRACT FROM AUTHOR]

Multiferroic BiFeO 3 -NiO (BFO-NiO) nanocomposites have been synthesized using sol-gel route and investigated via. the first principle DFT calculations, multiferroic-magnetoelectric response, and extremely low-temperature magnetic analysis. Powder X-ray diffraction (XRD) patterns along with Rietveld refinement data confirmed the phase purity viz. rhombohedral distorted perovskite BiFeO 3 - rock salt type NiO crystal structure and composite formation. Temperature dependent magnetic measurements confirmed the enhancement in the magnetism and the exchange bias effect due to the antiferromagnetic (AFM) and ferromagnetic (FM) exchange coupling interactions. Zero field cooled (ZFC) and field cooled (FC) magnetic results demonstrate the observation of typical superparamagnetic (SP) behavior for all the samples at room temperature whereas at low temperature a transition is reported from SP to quantum superparamagnetic (QSP) state through quantum tunneling of magnetic moment for all samples. Maximum polarization of 5.7μC/cm2 is observed for BFO-20% NiO composition. The noticeable change in the ferroelectric P vs E loops in the presence of external magnetic field confirm the evidence of multiferroic and magnetoelectric coupling behavior in the BFO-NiO nanocomposites. The DFT calculations have been done using WIEN2k software and found in well agreement with the reported experimental results. Further, the suitable temperature dependent magnetic squareness, evidence of considerable magnetoelectric coupling, exchange bias effect and SP nature make the BFO-NiO nanocomposites considerable suitable for various device applications such as information storage, magnetic random access memory, targeted drug delivery, magnetic resonance imaging (MRI), bio-sensing and tailoring other photocatalytic applications. [Display omitted] • Experiment and first principal DFT study of multiferroic-NiO nanocomposites. • Rietveld refinement data confirmed the phase purity. • Confirmation of exchange bias effect, super-paramagnetic behavior. • Ferroelectric and magnetic measurements confirm evidence of multiferroic and magnetoelectric coupling. • Magnetic squareness indicates information storage application. [ABSTRACT FROM AUTHOR]

Evidence for the suppression of collective magnetic behavior of dipolarly interacting Fe nanoparticles is found in Fe-Ag granular multilayers. Interaction of Fe particles separated by an Ag layer is studied as a function of the nominal thickness of the Ag layer. The surprisingly increasing interaction with increasing Ag-layer thickness, verified by memory-effect measurements, is explained by the formation of pinholes in the Ag layer at small Ag thicknesses, allowing direct ferromagnetic coupling between the Fe particles. This coupling may hinder the frustration of superspins favored by dipolar interactions. At larger Ag thicknesses, the Ag layer is continuous without pinholes and frustration leads to the appearance of the superspin-glass state. The effect of increasing interactions correlates well with the growing deviation at low temperatures of the measured field-cooled (FC) magnetization from the interaction-free FC curve calculated by a model based on the relaxation of two-level systems. Similar phenomenon is reported in a recently published paper (Sánchez et al., Small 2022 , 18, 2106762) where a dense nanoparticle system is studied. Here the collective magnetic behavior of the particles due to dipolar interactions is suppressed when the anisotropy energy of the individual particles exceeds a certain threshold. [ABSTRACT FROM AUTHOR]

• The crystal structure and superparamagnetism of γ-Fe 2 O 3 are discussed in detail. • Different preparation methods of γ-Fe 2 O 3 and their application scenarios are summarized. • The methods of γ-Fe 2 O 3 performance improvement are proposed. • The applications of γ-Fe 2 O 3 in different fields of environmental governance. Contaminant and pollutant have become increasingly prominent environmental issues. Photocatalysis is a promising way to remove various dyes and organic pollutants in waste water. As a potential photocatalyst, Fe 2 O 3 has a wide range of visible light absorption, good stability and recyclability, and has become an important material to degrade pollutants. Among them, γ-Fe 2 O 3 has attracted wide attention due to its suitable band gap, unique superparamagnetism and designable micromorphology, which has great potential to address the above issues. However, the rapid recombination of the carrier limits the further development of its application. This paper reviews the recent research progress of γ-Fe 2 O 3. Firstly, the crystal structure, superparamagnetism, optical properties and photocatalysis principle of γ-Fe 2 O 3 are introduced. Secondly, the synthesis methods of γ-Fe 2 O 3 are summarized, and the properties of γ-Fe 2 O 3 obtained by different methods are compared. The modification strategies of γ-Fe 2 O 3 based on morphology control, element doping and composite material preparation are summarized, and its applications in antibiotic degradation, heavy metal treatment, wastewater purification, microwave absorption, biomedicine and other fields are introduced. Finally, the application prospects and challenges of γ-Fe 2 O 3 in the environmental field are prospected, aiming to further prove the great potential of γ-Fe 2 O 3. It is hoped that the research results of this paper can provide some useful references for the development of high efficiency γ-Fe 2 O 3 -based catalysts, showing the great potential of γ-Fe 2 O 3 in the environmental remediation field. [ABSTRACT FROM AUTHOR]

The aim of this work consists in the use of cashew gum (Anacardium occidentale), a naturally occurring tropical specie from the Brazilian northeastern coast, for the synthesis of CoFe 2 O 4 (CF) and NiFe 2 O 4 (NF) nanoparticles. The structural, morphological and vibrational properties of nanoparticles were characterized by analytical and spectroscopic techniques such as X-ray diffraction (XRD), FTIR, Raman spectroscopy, TEM, SAED and TG. Magnetic properties were investigated through Mössbauer spectroscopy and DC magnetometry. The XRD results showed single phase nanoparticles with space group Fd-3m and crystallite size of 7.4 and 6.0 for CF and NF, respectively. TEM images showed agglomerated particles with mode sizes of 5.0 and 6.5 nm for CF and NF. SAED confirmed the crystalline spinel structure. The TGA and FTIR showed the presence of a carbonaceous material in the samples. FTIR and Raman spectroscopy demonstrated vibrational modes characteristic of metal‑oxygen bonds in the tetrahedral and octahedral sites. Magnetization measurements showed that both samples are superparamagnetic at 300 K. The Mössbauer spectra at 90 K showed the presence of single-phase CF and NF. • Cashew gum (Anacardium occidentale) is used for sol-gel synthesis. • Green synthesis of nanostructured single phases of Ni and Co ferrites • Structural, thermal, magnetic and spectroscopy characterization of ferrites [ABSTRACT FROM AUTHOR]

Pristine chromium oxide (Cr 2 O 3) and nickel ions (Ni2+) substituted Cr 2 O 3 nanoparticles were synthesized using a simple co-precipitation technique. The main objective of this work is to investigate Ni2+ substituent's role at different concentrations on the structural, morphological, optical, and magnetic properties of Cr 2 O 3 nanoparticles. Structural analyses based on X-ray diffraction (XRD), Raman and Fourier transform infra-red (FTIR) data confirmed the successful incorporation of Ni2+ into Cr 2 O 3 nanoparticles up to x = 0.05 of Ni2+ content, without affecting the rhombohedral crystal structure of Cr 2 O 3 nanoparticles. Rietveld refinement results showed the variation in lattice parameters and cell volumes alongwith the substitution of Ni2+ into Cr 2 O 3 nanoparticles. Raman and FTIR spectra also depicted a considerable shift in the characteristic vibration modes of Cr 2 O 3 nanoparticles due to strain-induced by Ni2+ substitution. Beyond x = 0.05, the structural transformation took place from rhombohedral to cubic crystal structure. Subsequently, new peaks (apart from Cr 2 O 3 phase modes) have been observed at x = 0.1 of Ni2+ content due to the formation of secondary phase i.e., nickel chromate (NiCr 2 O 4). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) illustrated the changes in the morphology of Cr 2 O 3 nanoparticles with Ni2+ substitution. UV–Vis analysis revealed a narrowing of optical band energy (E g) of Ni2+ substituted Cr 2 O 3 nanoparticles from 3 to 1.85 eV as Ni2+ content varies from x = 0 to 0.2, respectively. Afterward, there is an increase in optical band gap energy (E g) when Ni2+ content increased from x = 0.3 to 0.5, as NiCr 2 O 4 started dominating the Cr 2 O 3 phase. Single-phase Ni2+ substituted Cr 2 O 3 nanoparticles exhibited a superparamagnetic behavior, whereas the multi-phase compound ascribed to both superparamagnetic and paramagnetic. These changes in optical and magnetic properties can lead to novel strategies to render applications in the field of optoelectronics and optomagnetic devices. [ABSTRACT FROM AUTHOR]

The influence of quenching rate and nitrogenation in melt-spun Nd 1.2 Fe 10.6 Mo 1.4 has been investigated in terms of microstructure, phase formation and magnetic properties. Increasing the quenching rate leads to smaller grain size. However, it also implies a change in the crystallized phase structure. We obtained a pure ThMn 12 (1:12) structure at quenching rates up to 30 m/s, leading to an average grain size of 220 nm. Magnetic measurements of the as-spun ribbons revealed a reduction of the saturation magnetization for samples quenched above 30 m/s. This is attributed to the formation of a paramagnetic phase and/or magnetic phase with a Curie temperature (T C) close to room temperature which is confirmed by 57Fe Mössbauer spectroscopy. The analysis of the spectra rules out the presence of a ferromagnetic TbCu 7 (1:7) phase, which is usually reported in such system. The ribbons were nitrogenated in order to form the harder magnetic phase Nd 1.2 Fe 10.6 Mo 1.4 N x. The ribbon quenched at 30 m/s with the pure ThMn 12 nitride structure is the optimum sample for getting hard magnetic properties, with a coercivity of 0.6 T, saturation magnetization of 1.15 T and Curie temperature of 350 °C. Finally, we show the good stability of the later phase structure at elevated temperatures (≤ T C), making this compound a good candidate for permanent magnet applications. [ABSTRACT FROM AUTHOR]

The origin of magnetism in RF magnetron sputtered deposited carbon thin films is reported. Three different carbon thin films were deposited using RF magnetron sputtering of carbon target by Ar ions at RF power of 50 W, 100 W and 150 W, respectively. Microstructural characterization of films using Raman spectroscopy confirms the presence of graphitic crystallites in all three films and the crystallite edges are terminated with the sp3 bonding. However, increasing RF power results in an increase in graphitic crystallite size as well as the sp2/sp3 hybridization ratio, while the average density of the films decreases. The observed magnetization (measured using SQUID-VSM) in all the three-carbon films has a contribution from both superparamagnetic (SPM) particles (due to the interaction between unpaired spins) and the paramagnetic term due to isolated unpaired spins distributed throughout the film. The origin of experimentally observed magnetization in the carbon thin films and their correlation with the change in density and sp2/sp3 hybridization ratio due to variation in RF power is discussed. Image 1 [ABSTRACT FROM AUTHOR]

The discovery of ideal spin-1/2 kagome antiferromagnets Herbertsmithite and Zn-doped Barlowite represents a breakthrough in the quest for quantum spin liquids (QSLs), and nuclear magnetic resonance (NMR) spectroscopy plays a prominent role in revealing the quantum paramagnetism in these compounds. However, interpretation of NMR data that is often masked by defects can be controversial. Here, we show that the most significant interaction strength for NMR, i.e. the hyperfine coupling (HFC) strength, can be reasonably reproduced by first-principles calculations for these proposed QSLs. Applying this method to a supercell containing Cu-Zn defects enables us to map out the variation and distribution of HFC at different nuclear sites. This predictive power is expected to bridge the missing link in the analysis of the low-temperature NMR data. [ABSTRACT FROM AUTHOR]