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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]

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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]

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]

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]

(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]

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]

[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]

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]

[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]

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 electrical transport processes of zinc telluride (ZnTe) uniformly dispersed in reduced graphene oxide matrix (RGO-ZnTe composite) were investigated. It is observed from DC measurements that the charge transport process is consistent with Mott three dimensional variable range hopping (3D-VRH) in 85 K–280 K, confirmed by resistance curve derivative analysis (RCDA) method. AC conductivity indicates a Debye-like relaxation process caused by quantum mechanical tunneling (QMT) between localized sites in 90 K–473 K range. Magnetization data of RGO-ZnTe composite from SQUID and electron paramagnetic resonance (EPR) spectra show paramagnetic behaviour in 5 K–330 K despite the diamagnetism of pure RGO and ZnTe at room temperature. In photosensitivity, one order enhancement was observed in the RGO-ZnTe composite alongside three times higher reduction rate constant in photoreduction of aqueous pollutant 4-nitrophenol as compared to pure ZnTe. These significant increases in photocurrent and photoreduction efficiencies are attributed to dispersion of ZnTe on the 2D RGO surface indicating the synergy of ZnTe nanoparticle with RGO sheets. • DC conductivity reveals a conduction mechanism consistent with Mott three dimensional variable range hopping (3D-VRH) of charge carriers in 85 K–280 K. • DC measurement shows a crossover of charge transport mechanism from 3D-VRH (85 K–280 K) to Arrhenius behaviour (290 K–473 K). • AC conductivity suggests a Debye-like relaxation process caused by quantum mechanical tunneling (QMT) between localized states in 90 K–473 K. • RGO-ZnTe composite shows paramagnetic behaviour despite the diamagnetism in pure RGO and ZnTe. • One order enhancement of photosensitivity and three times improved photocatalytic reduction rate constant point to potential applications of RGO-ZnTe in optoelectronic device fabrication. [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]

Cobalt ferrite (CoFe 2 O 4) nanoparticles were prepared by chemical co-precipitation route at low temperature (70 °C). X-ray diffraction pattern confirms the cubic inverse spinel structure with an average crystallite size of ∼14 nm. Transmission electron microscopy exhibits a narrow distribution of particle size with an average particle size of 15 nm. The synthesized nanoparticles exhibited a saturation magnetization of 23.2 e m u / g and 33.6 e m u / g at 300 K and 20 K respectively. The randomly oriented spin layer thickness of 1.74 nm calculated at room temperature reduces the value of magnetization in as-synthesized nanoparticles. Exponential decay was observed in coercivity (H c) and remanence magnetization (M r) with the increase in temperature from 20 K to 300 K. Blocking temperature of 250 K is found from d (Z F C − F C) d t versus T curve. The plot of H H T versus T revealed the superparamagnetic behavior and exhibited largest superparamagnetic moment at 300 K. The effective anisotropy constant and surface anisotropy constant were calculated to be 6.00 × 104 J/m3 and 1.08 × 10−4 J/m2 respectively at blocking temperature. • Reduction in M s values with increasing temperature is attributed to the presence of non- magnetic surface layer and spin canting. • As synthesized single domain magnetic nanoparticles exhibited large magnetic moment per particle. • Dependence of superparamagnetic moment ((μ s p)) with temperature (T) and applied magnetic field (H) has been analysed systematically. • From vs. T graph, temperature ranges were measured for which as synthesized CoFe2O4 exhibits superparamagnetic behavior. • At 250 K and 300 K as synthesized CoFe2O4 nanoparticle exhibits superparamagnetic behavior with highest superparamagnetic moment 1.54 × 104 μB at T = 300 K. • The magnetic properties of cobalt ferrite nanoparticles synthesized in present work can be used as base ferrite materials environmental and biomedical applications. [ABSTRACT FROM AUTHOR]

MnFe 2 O 4 /ZnS magneto-fluorescent nanocomposite were synthesized by simple co-precipitation method and its structural, morphological, optical and magnetic characterization were done by XRD, HRTEM, FTIR and VSM techniques. The presence of MnFe 2 O 4 and ZnS in the nanocomposites was confirmed by XRD. Magnetic study shows that the nanoparticles manifest near superparamagnetic behaviour with a small coercivity of ∼66 G at room temperature and saturation magnetization significantly increases after coating ZnS on the surface of MnFe 2 O 4 core. The FTIR study confirms the incorporation of ZnS nanoparticles on the surface of MnFe 2 O 4 nanoparticles. PL spectra demonstrated the red shifted emission of nanocomposites as compared with that of pure ZnS. The heating efficiency of the nanocomposites is measured by its SAR and ILP values. This study exhibits the quantitative link between the sizes and saturation magnetization which is intimately intertwined with the heating efficiency of the nanoparticles. • Successfully synthesized MnFe 2 O 4 /ZnS Magnetic fluorescence nanocomposites. • The nanocomposites shows both magnetic and optical properties. • The nanocomposite shows high heating efficiency then ferrite nanoparticles for magnetic hyperthermia applications. [ABSTRACT FROM AUTHOR]

• Dilute AFM La 2 Fe 0.875 Cr 0.125 GaO 6 nanoparticles were prepared by sol-gel technique. • Crystallize in orthorhombic structure with Pbnm space group. • The particle size ranges from 28 to 62 nm. • Presence of non-interacting SPM clusters at room temperature. • Coercivity exhibits a maximum value of 6.694 kOe at ∼138 K. • Exhibits competing DM interaction and strong uncompensated surface spin effects. Magnetism at the nanoscale is intriguing, but that on the magnetic properties of a dilute antiferromagnetic (AFM) system is rarely studied. Presence of uncompensated spins at the lattice as well as on the nanoparticle surfaces could lead to interesting magnetic behaviour. We present the combined effect of reduction in particle size and dilution of exchange interactions on the magnetic properties of an AFM perovskite oxide. A dilute AFM compound, La 2 Fe 0.875 Cr 0.125 GaO 6 nanoparticles (average particle size ∼ 44.5 (7) nm), has been synthesized where non-magnetic Ga-ions are introduced to interrupt the superexchange pathways. The compound crystallizes in orthorhombic structure with Pbnm space group, where Fe, Cr and Ga ions are distributed randomly in the B-site. DC magnetic studies show superparamagnetic behaviour at room temperature, spin-flop transition and a prominent hysteresis loop with sufficiently high coercivity around 6.69 kOe at ∼138 K. The analysis of thermoremanent and isothermoremanent magnetization curves reveal SPM behaviour at 300 K and 2-dimensional dilute antiferromagnetic in field like nature at 5 K. AC magnetic susceptibility analysis confirms the presence of non-interacting clusters having SPM behaviour with blocking temperature ∼280 K. Furthermore, temperature variation of coercivity shows a Gaussian nature, mainly associated with competing Dzyaloshinskii-Moriya interactions between disordered B-site ions along with strong uncompensated surface spin effects. [ABSTRACT FROM AUTHOR]

• Various cations like, Mn, Co, Fe, Al are substituted for Ni in pristine LiNiO 2. • EXAFS confirms the presence of Jahn – Teller distortion in Ni3+ rich compositions. • 50% low spin Co3+ substitution at Ni-site shows super-paramagnetic ground state. • Whereas, non-magnetic Al3+ brings in competition between FM and AFM orders. We investigate the change in local crystal structure and its impact on the magnetic ground states of LiNi 0.5 X 0.5 O 2 (X = Mn, Co) and LiNi 0.75 Y 0.25 O 2 (Y = Fe, Al) and contrast it against LiNiO 2. The solid-state synthesis route adopted here introduces some anti-site disorder in the final compositions due to the volatile nature of Li ions. Powder X-ray diffraction (XRD) profiles were hence recorded using a rotating anode X-ray source to determine the percentage of anti-site disorder, and phase purity of all the compositions. Rietveld refinement of the XRD profiles confirms the symmetry and provides the estimation of unit cell parameters. Near-edge X-ray absorption spectra verified the oxidation state of various cations present in the compositions. Analysis of the extended X-ray absorption fine structure spectra identify the signatures of Jahn–Teller distortion in Ni3+ rich compositions. Changes in NiO 6 octahedral environment has a much deeper impact on the magnetism of these compositions. [ABSTRACT FROM AUTHOR]

Abstract Chromite nanospinels of M Cr 2 O 4 (M = Co, Zn, Mg and Cd) have been synthesized using a microwave combustion method. The spinel phase and average particles size have been investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both XRD and TEM reveal an overall average particle size of about 12 nm. UV–Vis optical absorbance measurements at room temperature indicate common wide optical energy gap of about 3.1–3.4 eV. Magnetization processes have been studied via precise field cooled (FC) and zero-field cooled (ZFC) magnetization measurements. The magnetic transition temperatures found in the nanoparticles are slightly below those of corresponding bulk crystals. Survived spiral spin textures below ∼26 K and coexisting spin-glassy state are observed in the Néel-type ferrimagnetic CoCr 2 O 4 nanocrystals with Curie temperature of 92 K. While the antiferromagnetic state of chromites with nonmagnetic divalent cations is observed in ZnCr 2 O 4 nanocrystals below Néel temperature of 11 K, it is significantly suppressed in MgCr 2 O 4 and CdCr 2 O 4 nanocrystals of identical average particle size. Our results indicate increased surface spins contribution with increasing lattice parameter. ESR linewidth and resonance field of M Cr 2 O 4 also show M -cation type dependence. The coexisting spin-glassy-like state in long-range ordered CoCr 2 O 4 and a possible superparamagnetic state in M Cr 2 O 4 (M = Zn, Mg and Cd) nanospinels are discussed as finite-size and Cr-Cr separation effects. Graphical abstract Image 1 Highlights • XRD, FTIR and TEM indicate single nanospinel phase of ∼12 nm in particle size. • Overall wide energy gap of ∼3.2 eV is demonstrated by UV–Vis optical measurements. • FIM CoCr 2 O 4 nanocrystals exhibit coexisting spin glassy and survived spiral spin states. • Varying suppression limit of the AF state in M Cr 2 O 4 (M = Zn, Mg, Cd) nanospinels is observed. • AF suppression is attributed to spin surface contribution depends on lattice parameter. [ABSTRACT FROM AUTHOR]

• Mn x Fe 3−x O 4 nanoparticles (x up to 1.5) were synthesized via coprecipitation process. • Lattice constants and particle size increase with Mn content. • Inversion grade of the spinal structure decreases with Mn content. • E g varies with Mn content due to competition between composition and size effects. • Magnetization's variation with Mn substitution follows their size variation. In this work, single phase Mn substituted magnetite (Mn x Fe 3−x O 4 , x = 0.25–1.50) nanoparticles were synthesized via a simple one-step capping agent-free co-precipitation route and characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared as well as UV–Vis spectroscopies, and vibrating sample magnetometer. The results showed that the lattice constants and particle size increase while the inversion grade of the spinal structure of the samples decreases with Mn content. It was found that the bang gap energy of the synthesized Mn ferrite nanoparticles varies with Mn substitution as a result of the competition between the chemical composition effect and the size effects, while in variations of their magnetization the size effects play the predominant role. [ABSTRACT FROM AUTHOR]

The present report is an investigation of morphological, structural and magnetic properties of multicomponent glass-ceramics with respect to content of nucleating agent (TiO 2) as well as thermal processing parameters. Structural features of these glass-ceramics were explored by their crystalline phase analysis and morphological studies after sintering at various temperatures (850–1000 °C) for 2 h (h). The samples exhibited near superparamagnetic nature which would be helpful for heat generation purposes (such as in hyperthermia treatment of cancer). Magnetic properties of the glass-ceramics are dependent on the crystallized phases grown upon sintering. Concentration dependent role of TiO 2 is discussed based upon the obtained results. • Effect of nucleating agent and thermal processing on properties of glass-ceramics is seen. • TiO2 helped to achieve better sintering of the glass-ceramics at lower temperatures. • Samples are nearly superparamagnetic due to limited growth of magnetic crystals. • These glass-ceramics may be useful for magnetic hyperthermia treatment of cancer. • TiO2 plays concentration dependent role in these glass-ceramics. [ABSTRACT FROM AUTHOR]

Abstract The comprehensive investigation of Raman modes, magnetic and dielectric properties have been carried out on Mn-Co co-doped SnO 2 nanoparticles by fixing Mn content (5%) and varying doping concentration of Co (0%, 1%, 3%, and 5%). Average crystallite size estimated from Williamson Hall analysis is found to be in decreasing order on increasing concentration of Co and ranging between 29.4 nm and 19.2 nm. Transmission electron microscopy analysis gives evidence that the pre-synthesized Mn-Co co-doped SnO 2 powder samples contain nanoparticles with particle size 24.5 nm for 5% Mn doped SnO 2 and 14.5 nm for 5% Mn + 5% Co co-doped SnO 2. These nanoparticles exhibit a very strange ferromagnetic to superparamagnetic transition and superparamagnetic phase of the samples grows on increasing Co content. This improved superparamagnetic phase in Mn-Co co-doped SnO 2 nanoparticles may offer ferrofluids and several biomedical applications like MRI, drugs delivery, hyperthermia, etc. The origin of electric polarization in the Mn-Co co-doped SnO 2 nanoparticles has been explained on the basis of dielectric permittivity and typical dielectric dispersion. The small polaron hopping and correlated barrier hopping was found as a dominating ac conduction mechanism in 5% Mn doped SnO 2 and heavily co-doped (5% Mn + 5% Co) SnO 2. The typical behavior of increasing ac activation energy in Mn-Co co-doped SnO 2 samples with frequencies have also been depicted. Highlights • Mn-Co co-doping strongly influenced the position and intensity of the peaks of the Raman spectrum of SnO2. • Increasing defects with increasing temperature appreciably enhanced the space charge polarization. • Ac conduction has been increased with increasing temperature in Mn-Co co-doped SnO2. • Ferromagnetic to superparamagnetic transformation in Mn-Co co-doped SnO2 was observed. [ABSTRACT FROM AUTHOR]

Highlights • Superparamagnetic zinc ferrite nanoparticles were synthesized by hydrothermal method. • The particles size of the nanoparticles increased as the reaction time increased. • The nanoparticles show superparamagnetic behavior with zero H c and M r. • A considerably high M max value was obtained at this particle size limit. • The mean particle sizes and hence high M max can be tuned by adjusting the reaction time. Abstract Superparamagnetic zinc ferrite nanoparticles with high magnetization were successfully synthesized by hydrothermal method at 110 ° C under different reaction times from 2 to 24 h. Elemental analysis of the nanoparticles determined by inductively coupled plasma atomic emission spectroscopy and energy dispersive X-ray spectrometer results proved that the samples are zinc ferrite. X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy analysis displayed that zinc ferrite nanoparticles were single phase of cubic ferrite. The particles size, d XRD of the nanoparticles calculated from XRD patterns increased as the reaction time increased. From the images of transmission electron microscopy (TEM), the particle sizes, d TEM were also calculated and increased from 6.8 ± 2.5 to 10.6 ± 5.1 nm as the reaction time increased, which were consistent with the d XRD. Magnetic measurements revealed that the magnetization curves of the synthesized nanoparticles show superparamagnetic behavior with zero coercivity and remanence. And, the magnetization values also increased to a maximum value of 30.8 emu/g (measured at 20 kOe) as the particle size increased to ∼10 nm with the increase of reaction time. At this particle size limit, this is a considerable high value compared to the superparamagnetic zinc ferrite nanoparticles studies. Magnetization values were also extrapolated. It is seen that to a certain degree, the average particle sizes of the products and hence high maximum magnetization can be tuned by simply adjusting the parameter, reaction time by hydrothermal process. [ABSTRACT FROM AUTHOR]

Abstract Tetragonal, scheelite-type Pb 1–3x □ x Gd 2x (MoO 4) 1–3x (WO 4) 3x materials (x = 0.0455, 0.0839, 0.1154, 0.1430, 0.1667 and 0.1774, where □ denotes vacancies) synthesized via solid state reaction route were magnetically and electrically examined. The ac and dc magnetic measurements as well as the Brillouin fitting procedure showed paramagnetic state with characteristic superparamagnetic-like behaviour and a spin-only contribution to the paramagnetic moment. Broadband dielectric spectroscopy studies exhibited existence in the loss spectra the faster and slower relaxation processes with various time scales for the gadolinium-poorer samples with the x vacancy parameter up to 0.1154. For samples with higher Gd content, i.e. when x > 0.1154, no signs of any relaxation processes was observed. This phenomenon has been explained by a smaller number of structural and spin defects as opposed to the samples poorer in gadolinium ions. [ABSTRACT FROM AUTHOR]

Abstract The rhombohedral perovskite LaAl 0.5 Ni 0.5 O 3 (or La 2 AlNiO 6), synthesized by a combustion method is found to contain Al3+ and Ni3+ cations in the rhombohedral lattice. The material exhibits a temperature dependent (thermally excited) paramagnetic susceptibility and follows the modified Curie-Weiss law implying an antiferromagnetic ordering at very low temperatures. A non-saturating hysteresis loop with a coercivity of 108 Oe is observed at 2 K which is arising from the magnetic contribution from Ni in the lattice. The conduction mechanism in LaAl 0.5 Ni 0.5 O 3 for 80–300 K follows the Mott's variable range hopping mechanism. A negative magnetoresistance of 1.75% is observed at 2 K under 90 kOe field which decreases linearly by increasing the temperature up to 18 K and then changes to positive with comparatively low value. Both the negative and positive magnetoresistance increases linearly with an applied magnetic field. Highlights • The rhombohedral perovskite LaAl 0.5 Ni 0.5 O 3 with Al3+ and Ni3+ cations at the B-site is synthesized by a combustion method. • A temperature dependent (thermally excited) paramagnetic susceptibility is observed that follows the modified Curie-Weiss law. • The conduction mechanism follows the Mott's variable range hopping mechanism. • A negative magnetoresistance of 1.75% is observed at 2 K under 90 kOe field. [ABSTRACT FROM AUTHOR]

Highlights • (Mn, Co) co-doped SnO 2 nanoparticles are fabricated by the CPACP technique. • Enhanced magnetization is fulfilled in the co-doped system. • Transition from ferromagnetism to paramagnetism is observed in the co-doped system. • The excessively Mn doping leads to a diamagnetic behavior. Abstract Co and Mn-Co co-doped SnO 2 nanoparticles have been successfully synthesized using a simple technique called as citrate precursor assisted co-precipitation (CPACP). Structural and compositional analyses by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Energy Dispersive X-Ray Fluorescence Spectrometer (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed that Co and Mn ions were incorporated into the SnO 2 host lattice without changing the inherent rutile structure. The average crystallite size of the prepared samples were estimated to be in the range of 8–12 nm. In a single Co2+-doped SnO 2 sample, the magnetization was observed to increase as the Co2+ ions concentration increased. The transition metal Mn can adjust the magnetic signal of the Co2+-doped SnO 2 sample, which is subject to the concentration of Mn dopant. Adding a proper amount of Mn to the Co2+-doped SnO 2 sample enhanced the magnetization. As the Mn2+ ions concentration increases, the magnetic properties of the (Mn, Co) co-doped SnO 2 nanoparticles gradually shift from ferromagnetic behavior to superparamagnetism. However, the sample Sn 0.83 Mn 0.12 Co 0.05 O 2 exhibits diamagnetic behavior when the concentration of Mn2+ ions is doped excessively. [ABSTRACT FROM AUTHOR]

Abstract Bulk cobalt ferrite, being a hard ferrite, shows high magnetization, high resistivity and high coercivity. If thin films of cobalt ferrite can be deposited at a low enough temperature and if its coercivity can be reduced, cobalt ferrite will make a very good candidate for use as a magnetic core of an integrated inductor in RF-CMOS ICs. Though polycrystalline and epitaxial thin films of cobalt ferrite have been made by various techniques, there are no reports of thin films of superparamagnetic cobalt ferrite. In this work, nanocrystalline cobalt ferrite thin films, which are superparamagnetic as deposited, have been prepared in the solution medium at ∼190 °C, using microwave irradiation. The as-prepared films have a saturation magnetization (M S) of 401 emu/cc and coercivity (H C) of 19 Oe at room temperature for a crystallite size of 2 nm. The cobalt ferrite powder obtained as a by-product during the same process has M S of 50 emu/g and H C of 5 Oe at room temperature, making it superparamagnetic. The as-prepared films were annealed in air at 300 °C for 5 min and 10 min. Annealing for 10 min results in an increase in crystallite size to 36 nm, M S increases from 401 emu/cc to 545 emu/cc, and H C increases from 19 Oe to 860 Oe. The change in magnetic properties can be directly associated with change in the crystallite size and degree of crystallographic inversion, as determined by neutron diffraction and deduced from X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Graphical abstract Four tetracoordinate Ni(II) complexes have been prepared, structurally characterized, and subjected to magnetometric studies. The complexes [Ni(PPh 3) 2 (NCS) 2 ], [Ni(dppp)(NCS) 2 ], and [Ni(dppm)Br 2 ] are planar and thus diamagnetic. The complex [Ni(biqu)Br 2 ] is pseudotetrahedral, with the geometry close to C 2v symmetry, and paramagnetic. Highlights • Four tetracoordinate Ni(II) complexes have been prepared. • Three complexes are planar and diamagnetic. • One complex is pseudotetrahedral and paramagnetic. • It exhibits a ZFS of the ground term described by D and E parameters. • The GCFT and ab initio calculations confirm this interpretation. Abstract Four tetracoordinate Ni(II) complexes have been prepared, structurally characterized, and subjected to magnetometric studies. The complexes [Ni(PPh 3) 2 (NCS) 2 ], [Ni(dppp)(NCS) 2 ], and [Ni(dppm)Br 2 ] are planar and thus diamagnetic. The complex [Ni(biqu)Br 2 ] is quasi-tetrahedral, with the geometry close to C 2v symmetry, and paramagnetic. While on one side it resembles a prolate bisphenoid (the angle N-Ni-N = 83 deg), on the second side it mimics an oblate bisphenoid (Br-Ni-Br = 126 deg). It exhibits a zero-field splitting of the ground term 3A 2 into three crystal-field multiplets that can be described by D and E parameters within the spin Hamiltonian formalism. The ab initio calculations confirm this interpretation; however, the evaluation of the spin-Hamiltonian parameters meets difficulties owing to the quasi-degeneracy of the electronic terms. [ABSTRACT FROM AUTHOR]

Abstract The MAB phases are ternary, atomically laminated compounds that crystallize with orthorhombic structures and consist of transition metal (M) boride sublattices interleaved with single or double layers of Al. To date, the magnetic properties of ferromagnetic Fe 2 AlB 2 have been well-studied experimentally, but those of most end member MAB phases with other transition metals remain poorly understood. Herein, predominantly single-phase Cr 3 AlB 4 and Cr 2 AlB 2 powders, with minor amounts of CrB impurities, were synthesized by heating mixtures of chromium monoboride (CrB), aluminum (Al), and boron or CrB and Al under flowing Ar. These reactants were found to substantially suppress the formation of undesired phases in the Cr-Al-B system. The magnetic properties of Cr 3 AlB 4 , Cr 2 AlB 2 and CrB powders were characterized. All compounds exhibit paramagnetic behavior down to 4 K, with susceptibilities that are quite weakly temperature dependent at higher temperatures and a Curie-Weiss-like component prominent at low temperatures. Magnetization isotherms of the three compounds, showed approximately linear behavior above 5 kOe and no saturation of the magnetic moment up to 40 kOe, which is consistent with paramagnetism. The magnitude of the magnetic moments showed little variation with composition, on a per Cr atom basis. While the exact nature of the Curie-Weiss component is not entirely clear, we tentatively attribute it to dilute extrinsic impurities. Highlights • Cr 2 AlB 2 and Cr 3 AlB 4 are synthesized as predominantly single-phase powders. • Magnetization and heat capacity studies suggest Pauli-like paramagnetic behavior. • STEM imaging shows atomic structure and defects in Cr 3 AlB 4 for the first time. [ABSTRACT FROM AUTHOR]

The search for materials that can bear the increasingly abrupt conditions imposed to electronic devices in computers and other systems has intensified. Materials that are sensitive to variations in magnetic fields and resistant to sharp variations in temperature are desirable. To achieve such materials, several sample preparation methods have been employed. Most of these methods rely on the mechanical systems of mixtures and usually require significant discharge temperatures. In particular, the sol-gel method is quite promising because it allows for direct control of the structure and morphology of the material in all stages of the synthetic procedure. In this study, we have doped a titanium oxide matrix with manganese chloride, which afforded a material with a paramagnetic phase. Results from our investigation into the relationship between magnetic susceptibility and temperature, obtained from measurements in a superconducting quantum interferometer device (SQUID), pointed to the great sensitivity of the prepared material to low-intensity magnetic fields for temperature. [ABSTRACT FROM AUTHOR]

Nanocrystalline GdFeO 3 and Gd 3 Fe 5 O 12 powders were prepared successfully by sol–gel auto-combustion method using a glycine-based gel. The as-prepared GdFeO 3 and Gd 3 Fe 5 O 12 powders presented spherical shape, and composed of continuous porous network structure due to the releasing of a large amount of gases during auto-combustion process. This special microstructure was significant for reducing the magnetic interactions between nanocrystalline powders. The Gd 3 Fe 5 O 12 samples presented ferrimagnetic feature at low temperatures. At 10 K, the saturate magnetization is about 87.9 emu/g. As temperature increased to 300 K, the magnetization decreased rapidly since the thermal fluctuations changed the main magnetic spin ordering. The GdFeO 3 samples presented antiferromagnetic feature at 5 K, and the magnetization reaches 109 emu/g at 50,000 Oe field. As temperature increased to 300 K, the antiferromagnetism decreased rapidly, and the magnetization curve presents linear tendency due to the dominant paramagnetism contribution of Gd 3+ ions. [ABSTRACT FROM AUTHOR]

A new intermetallic compound, ternary antimonide Eu 7 Cu 44 Sb 23-δ [ Fm -3m, a  = 17.4346(1)Å, δ = 0.5(1)] is reported. The compound forms a continuous substitutional solid solution with its Eu 7 Cu 44 As 23 archetype. The gradual substitution of Sb for As evokes partial disorder in the copper–pnictogen framework that becomes more pronounced with an increase of the Sb content and changes magnetic properties. Whereas Eu 7 Cu 44 As 23 is metallic ferromagnet below 17 K, Eu 7 Cu 44 Sb 23-δ shows paramagnetic behavior down to 1.8 K according to the magnetic measurements, while retaining metallic properties according to the DFT calculations. The origin of the disorder, the structure-property relationships, as well as prospects of further substitution in the anionic sublattice are discussed. [ABSTRACT FROM AUTHOR]

In the present work, we have studied the magnetic properties of magnetic bilayer Kekulene structure with mixed spin-5/2 and spin-2 Ising model using Monte Carlo study. The magnetic phase diagrams of mixed spins Ising model have been given. The thermal total, partial magnetization and magnetic susceptibilities of the mixed spin-5/2 and spin-2 Ising model on a magnetic bilayer Kekulene structure are obtained. The transition temperature has been deduced. The effect of crystal field and exchange interactions on the this bilayers has been studied. The partial and total magnetic hysteresis cycles of the mixed spin-5/2 and spin-2 Ising model on a magnetic bilayer Kekulene structure have been given. The superparamagnetism behavior is observed in magnetic bilayer Kekulene structure. The magnetic coercive field decreases with increasing the exchange interactions between σ-σ and temperatures values and increases with increasing the absolute value of exchange interactions between σ-S. The multiple hysteresis behavior appears. [ABSTRACT FROM AUTHOR]

A series of (Sr 0.6 Ca 0.4 ) (Co y Mn 1-y ) O 3 (0.2 ≤ y ≤ 1.0) ceramic were synthesized by the simple cost effective chemical co-precipitation method. X-ray diffraction analysis show that all samples having orthorhombic crystal structure. Replacement of Mn by Co plays an important role in changing the magnetic properties. The (Sr 0.6 Ca 0.4 ) (Co y Mn 1-y ) O 3 (0.2 ≤ y ≤ 1.0) ceramic shows Paramagnetic to Antiferromagnetic (PM-AFM) transition, at temperature T = 175 K. Negative magnetization is observed for all samples except Co = 1.0. [ABSTRACT FROM AUTHOR]

Structural, dielectric and magnetic properties of dense Dy-substituted strontium titanate ceramics are investigated. In the Sr 1-1.5 x Dy x TiO 3 system, incorporation of Dy onto the Sr site is confirmed by a linear decrease of the lattice parameter up to x = 0.05. Dielectric spectroscopy analysis of Sr 1-1.5 x Dy x TiO 3 ceramics reveals four relaxations. Two relaxations observed below 55 K are attributed to dipoles formed by off-centre displacement of Dy 3+ ions on the Sr sites. Other two dielectric relaxations found at higher temperatures are attributed to the oxygen vacancy related mechanisms. As result, very high dielectric permittivity of ∼33500 at 28 K and of ∼9600 around room temperature at moderate dissipation factor of ∼0.02 are obtained for Sr 0.985 Dy 0.01 TiO 3 ceramics, making it a promising material for capacitor electronic applications. Paramagnetic behaviour observed for Sr 1-1.5 x Dy x TiO 3 as well as for Sr 1- x Dy 2 x Ti 1- x O 3 ceramics indicates impossibility to induce a magnetic order and hence magnetoelectric coupling in strontium titanate by Dy substitution. [ABSTRACT FROM AUTHOR]

• Polycrystalline specimens of Ba 2 Y 1- x Cu x TaO 6-δ were synthesized by the solid-state reaction route. • The magnetic properties of the Ba 2 Y 1- x Cu x TaO 6-δ solid solutions were investigated and reported for the first time. • The Cu for Y substitution induces paramagnetism and the onset of antiferromagnetic correlations. We carried out a study of the structural and magnetic properties of Ba 2 Y 1- x Cu x TaO 6- δ (0.0 ≤ x ≤ 0.5) compounds. The cubic rock-salt double perovskite structure of Ba 2 YTaO 6 is retained upon the partial substitution of Cu for Y up to x = 0.50 and the lattice parameter a drops at the rate of da/dx ≈ −0.17 ± 0.01 Å/%Cu. While the effective moment μ eff and the Curie-Weiss temperature θ CW are nearly negligible in Ba 2 YTaO 6 , the partial substitution of Cu for Y results shows an increase in μ eff at the rate of ≈ 1.9 ± 0.2 µ B /%Cu, consistently with the paramagnetic behavior expected for Cu2+, and a decrease in θ CW at the rate of −16 ± 2 K/%Cu. The drive of θ CW towards more negative values is suggestive of the onset of antiferromagnetic correlations. [ABSTRACT FROM AUTHOR]

The phase structure and magnetic properties of magnetite-based glass-ceramics obtained by crystallization of Fe-containing boroaluminosilicate glass melts are presented. The use of Cr 2 O 3 as nucleating agent generated magnetite configurations showing a complex temperature dependence of the relaxation of the remanent magnetization. Specifically, the expected decrease in time of the remanent magnetization occurs only in a limited temperature range, whereas it increases at low and high temperatures (upward relaxation). We tentatively attribute these effects to the complex spin structure of the tiny magnetite nanoparticles, their complex size distribution and the interplay between the relaxation mechanisms in different temperature ranges. [ABSTRACT FROM AUTHOR]

We have studied the effect of replacing Mn 3+ by Cr 3+ on the structure, transport and magnetism in the bilayered manganite LaSr 2 Mn 2 O 7 . Although no structural transition was observed in LaSr 2 Mn 2−y Cr y O 7 (0.1 ≤ y ≤ 0.6), the electrical transport and the magnetic properties were found to be affected significantly by this substitution. Substitution of Cr 3+ reduces the conductivity by restricting the hopping of small polarons. Magnetization increases with increasing Cr 3+ concentration suggesting that Cr 3+ -ions induce ferromagnetic moments . The ferromagnetic and an antiferromagnetic phase observed above ∼60 K merge into an inhomogeneous phase below this temperature. Thermopower yields an essentially concentration independent charge density nearly equal to its value for chromium free composition inspite of its expected decrease with this substitution suggesting that the small charge density of the insulating AFM phase is supplemented by the free carriers in the FM phase. The inhomogeneous phase shows a relaxor type behavior which contrasts with the spin glass behavior seen in La 0.46 Sr 0.54 Mn 0.98 Cr 0.02 O 3 having an identical AFM magnetic state. The difference is attributed to the non-JT character of Cr-ions which reduce the distortion of the Mn O octahedra located within the FM domains. With a higher lattice strain in the surrounding AFM matrix the carriers remain confined within the FM domains leading to the relaxor type behavior. [ABSTRACT FROM AUTHOR]

Hyperthermia cancer atherapy designed by magnetic particles as heating nano-mediators has been greatly applied for in vitro purposes to make reliable and certain conditions for in vivo trials. This intracellular treatment has found higher efficiency as compared to conventional ones due to generating heat locally through superparamagnetic nanoparticles for inaccessible tumors with minimal damage to the healthy cells nearby. The main challenges of this novel cancer therapy are the enhancement of heating power of such nanoparticles and the control of the local tumoral temperature. Those hyperthermia factors basically derived from magnetic nanoparticles as well as magnetic field. Thereby, the efficiency of magnetic hyperthermia is principally dependent on the proper determination of their features. This study tried to provide a comprehensive evaluation on the magnetic hyperthermia therapy through the determination of magnetic nanoparticles such as surface chemistry, intrinsic and extrinsic magnetic properties. In addition, the features of the magnetic field that substantially play on induction heating power and hyperthermia temperature are reviewed. [ABSTRACT FROM AUTHOR]

Biocompatible ferrofluids based on dextran coated iron oxide nanoparticles were fabricated by conventional co-precipitation method. The experimental results show that the presence of dextran in reaction medium not only causes to the appearance of superparamagnetic behavior but also results in significant suppression in saturation magnetization of dextran coated samples. These results can be attributed to size reduction originated from the role of dextran as a surfactant. Moreover, weight ratio of dextran to magnetic nanoparticles has a remarkable influence on size and magnetic properties of nanoparticles, so that the sample prepared with a higher weight ratio of dextran to nanoparticles has the smaller size and saturation magnetization compare with the other samples. In addition, the ferrofluids containing such nanoparticles have an excellent stability at physiological pH for several months. Furthermore, the biocompatibility studies reveal that surface modification of nanoparticles by dextran dramatically decreases the cytotoxicity of bare nanoparticles and consequently improves their potential application for diagnostic and therapeutic purposes. [ABSTRACT FROM AUTHOR]

Effect of Mn substitution on the structural, optical, surface and magnetic properties of mixed LaFeO 3 i.e. La Ce nanoferrites (La 0.9 Ce 0.1 Fe 1-x Mn x O 3 ) synthesized by hydrothermal route using ionic liquid surfactant (ILS), 1-hexadecyl-3-methyl imidazolium chloride, [C 16 mim][Cl], have been explored by X-ray diffraction (XRD), IRaman spectroscopy, Brunauer-Emmett-Teller (BET) adsorption isotherm, Vibrating sample magnetometer (VSM) and Mӧssbauer spectroscopy etc. Incorporation of Mn in crystal lattice of La Ce ferrite induced the structural distortion as specified by structural studies. Morphology and the size of the obtained nanoparticles (NPs) get slightly altered by the quantity of dopant as observed from transmission electron microscopy (TEM). The appearance of rod shaped morphology along with spherical NPs indicates the templating effect of ILS. Surface and magnetic properties of Mn doped La Ce NPs have found to be significantly improved than that of undoped La Ce ferrites. Magnetization of the obtained NPs strongly depends on the content of Mn in the lattice. Enhanced magnetization has been observed up to certain extent of Mn doping (x = 0.3). At higher Mn content (x = 0.5), a significant reduction in magnetization has been observed as revealed from Mӧssbauer and magnetic studies. The enhanced surface area (36.18 m 2 /g) of the Mn doped samples over the undoped La Ce ferrite opens the new doors in biological and sensing applications. [ABSTRACT FROM AUTHOR]

Nano-sized manganese ferrite (MnFe 2 O 4 ) particles were prepared using co-precipitation method in two different pH (9 and 11). The structural, morphological, optical and magnetic properties of as-synthesized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis absorption and vibrating sample magnetometer (VSM). The FTIR spectra revealed two strong peaks at about 600 and 400 cm −1 that can be attributed to the vibration mode of octahedral and tetrahedral sites of spinel structure of MnFe 2 O 4 , respectively. The XRD results showed that the nanocrystalline MnFe 2 O 4 has pure cubic spinel crystal structure with average crystallite size of 11 nm. The cation distribution of these nanoparticles was estimated by X-ray analysis data. The blue shift was observed in the band gap when compared with bulk sample which is due to the quantum size effect. The absence of hysteresis for MnFe 2 O 4 nanoparticles indicated the superparamagnetic behaviour, as expected for single domain nanoparticles. The obtained value for saturation magnetization being less than its value of bulk ones and larger pH is due to surface effects. The calculated magnetic particle size was smaller than crystallite size estimated from the XRD results; which indicate the presence of dead layer on particle surface. [ABSTRACT FROM AUTHOR]

New experimental results on the pressure dependence of magnetic susceptibility χ of SmS in semiconducting phase are obtained with precise measurements of χ as a function of the hydrostatic pressure P up to 2 kbar at liquid nitrogen and room temperatures. A pronounced magnitude of the pressure effect is found to be positive in sign and strongly temperature dependent: the pressure derivatives of χ , d ln χ /d P , are 6.3 ± 0.5 and 14.2 ± 1 Mbar −1 at 300 and 78 K, respectively. The experimental results are supplemented by theoretical calculations of the volume dependent electronic structure of SmS and orbital magnetism of the band electronic states χ VV(band) . It was found that χ VV(band) value appeared to be strongly dependent on pressure, determining the main mechanism of the observed puzzling pressure effects in semiconducting SmS compound. [ABSTRACT FROM AUTHOR]

The discovery of colossal magnetoresistance (CMR) in perovskite manganites has attracted considerable interest due to their utilisation in spintronic devices. Various techniques were adopted to investigate the influence of their particle size on magnetic and transport properties. Unfortunately, the complexity of conventional methods underlines the need for a simple preparation technique. Here, single phase Nd 0.7 Sr 0·3 MnO 3 (NSMO) was successfully synthesised by thermal treatment method with polyvinylpyrrolidone (PVP) acting as capping agent. FTIR spectra confirmed the decomposition of PVP after a high-temperature sintering process. The atomic composition of the sample was found very close to the nominal ratio. NSMO exhibited paramagnetism at room temperature, and its T C was recorded at 246 K. Typical CMR behaviour was perceived and accompanied by metal-insulator transition (T MI) at 182 K. Thus, this study has provided a novel approach to prepare high-purity Nd-based manganite with an easier operation. • A single-phase NSMO manganite was synthesised by thermal treatment method. • PVP was used as capping agent and decomposed after the sintering process. • Typical colossal magnetoresistance (CMR) behaviour was observed. [ABSTRACT FROM AUTHOR]

This article reviews magnetic memory effects in spin-glasses (SG), superspin-glasses (SSG) and superparamagnetic (SPM) materials with detailed discussions about protocols and mechanisms. The origin of time (t) and temperature (T) dependent magnetic memory effects in different classes of materials have been discussed starting from the nanoscale towards the bulk magnetism. Magnetic memory effects (T and t dependent) in field cooled (FC) and zero field cooled (ZFC) protocols are focused to understand the physics of ageing and rejuvenation in SG, SSG and SPM materials. The article is enlightened with significant discussion to understand the diverse nature and classified properties of magnetic memory of the said materials. • M emory effects in SG (both in bulk and nano) and SPM materials. • Origin, footprint and diverse characteristics of memory effect. • Significantly covers the field of magnetism especially magnetic metastabilities. • Diverse nature and classified properties of magnetic memory. [ABSTRACT FROM AUTHOR]

Nanostructured magnetic materials with the chemical composition CoFe 2 O 4 and CoCr 0.9 Fe 1.1 O 4 were synthesized through Citrate-gel chemical synthesis with a crystallite size of 6.5 nm and 10.7 nm respectively. Structural characterization of the samples was performed by X-ray diffraction analysis and magnetic properties were studied using Vibrating Sample Magnetometer (VSM). Magnetization measurements as a function of applied magnetic field ±10 T at various temperatures 5 K, 25 K, 310 K and 355 K were carried out. Field cooled (FC) and Zero field cooled (ZFC) magnetization measurements under a magnetic field of 100 Oe for temperature ranging from 5–400 K were studied. The blocking temperature ( T b ) for both the ferrites was observed to be around 355 K. Below blocking temperature they showed ferromagnetic behavior and above which they are superparamagnetic in nature that favors their application in the biomedical field. The substitution of paramagnetic Cr 3+ ions for magnetic Fe 3+ ion in cobalt ferrite has resulted in a decrease in magnetization and the coercivity of the samples. CoCr 0.9 Fe 1.1 O 4 nanoferrites with observed low coercivity of 338 Oe make them desirable in high frequency transformers due to their very soft magnetic behavior. [ABSTRACT FROM AUTHOR]

The mechanical and magnetic properties of Ni-Fe alloy deposits may be controlled by compositional tailoring and reinforcement by ceramics. The incorporation of high content of ceramic particles in the alloy matrix has, however, detrimental effect on electrical and magnetic properties of the nanocomposites. Here, electrodeposition of WO 3 nanoparticle (spheroidal shaped, 20–40 nm) doped Ni-Fe nanocomposites has been carried out in an organic bath at various current densities. The particle content in coating was found up to ~ 2.0 wt%. Field emission scanning electron microscope (FESEM), energy dispersed X-ray analyzer (EDAX) and atomic force microscopic (AFM) examinations revealed a distinct change in morphology of the deposit due to inclusion of the particles in the matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed fcc lattice of the matrix and a shift in preferred orientation of the coating from (111) to (220) crystallographic planes with increasing current density. Significant enhancement in the microhardness of the coatings was observed on incorporation of only 1.25 wt% WO 3 particles due to solid solution hardening and dispersion hardening. An improvement in the conduction and corrosion resistance of the coatings over matrix has also been noticed due to dispersion of the ceramic particles in the matrix. Magnetic studies point to ferromagnetic behavior of the nanocomposite which also has the tendency of superparamagnetism. [ABSTRACT FROM AUTHOR]