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Zinc ferrite (ZnFe2O4) nanoparticles were prepared by chemical co-precipitation method. Structural characterization was performed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Formation of spinel phase was confirmed from XRD studies. Crystallite size and lattice constant of the prepared sample were calculated. TEM images reveal spherical-shaped particles with nanosized distribution. Room temperature magnetic hysteresis loop was recorded using vibrating sample magnetometer (VSM). The magnetization loops exhibit a very narrow loop and behave like superparamagnetic nature. Using the Langevin function, the magnetic behaviour of the prepared nanoparticles was investigated. From the curve fitting, saturation magnetization and reduced magnetization were determined. As-prepared sample was further annealed at three different temperatures namely 800 °C, 1000 °C, and 1200 °C for 2-h duration. The effects of annealing on the structural and magnetic properties were further investigated using XRD and VSM. The observed results on the magnetic characteristics of ZnFe2O4 and applicability of the Langevin function are being discussed.

ARTÍCULO RETRACTADO Las nanopartículas magnéticas de magnetita (MNP) presentan comportamiento superparamagnético, lo que les confiere propiedades importantes como bajo campo coercitivo, fácil modificación superficial y niveles de magnetización aceptables. Esto las hace útiles en técnicas de separación. Sin embargo, pocos estudios han experimentado con las interacciones de las MNP con campos magnéticos. Por tanto, el objetivo de esta investigación fue estudiar la influencia de un campo magnético oscilante (CMO) en columnas monolíticas poliméricas con nanopartículas magnéticas vinilizadas (VMNP) para cromatografía líquida capilar (cLC). Para ello, se sintetizaron MNP mediante coprecipitación de sales de hierro. La preparación de las columnas monolíticas poliméricas se realizó por copolimerización y la agregación de VMNP. Aprovechando las propiedades magnéticas de las MNP, se estudió la influencia de los parámetros como frecuencia de resonancia, intensidad y tiempo de exposición de un CMO, aplicado a las columnas sintetizadas. Como resultado se obtuvo una mejor separación de una muestra según los parámetros medidos, de modo que se logró una resolución de la columna (Rs) de 1,35. Las propiedades morfológicas de las columnas fueron evaluadas mediante microscopía electrónica de barrido (SEM). Los resultados de las propiedades cromatográficas revelaron que la mejor separación de la muestra de alquilbencenos se da en condiciones de 5,5 kHz y 10 min de exposición en el CMO. Este estudio constituye una primera aplicación en técnicas de separación cromatográficas para futuras investigaciones en nanotecnología.

Due to their non-toxicity and their ability to be functionalized, magnetite (Fe3O4) nanoparticles (NPs) are good candidates for a variety of biomedical applications. To better implement their applications, it is crucial to well understand the basic structural and magnetic properties of the NPs in correlation with their synthesis method. Here, we show interesting properties of Fe3O4 NPs of various sizes ranging from 5 to 100 nm and the dependence of these properties on particle size and preparation method. One synthetic method based on heating Fe(acac)3 with oleic acid consistently gives 5 ± 1 nm NPs. A second method using the thermal decomposition of Fe(oleate)3 in oleic acid led to larger NPs, greater than 8 nm in size. Increasing the amount of oleic acid caused the average NP size to slightly increase from 8 to 10 nm. Increasing both the reaction temperature and the reaction time caused the NP size to drastically increase from 10 to 100 nm. Powder X-ray diffraction and electron-microscopy imaging show a pure single crystalline Fe3O4 phase for all NPs smaller than 50 nm and spherical in shape. When the NPs get larger than 50 nm, they notably tend to form faceted, FeO core–Fe3O4 shell structures. Magnetometry data collected in various field-cooling conditions show a pure superparamagnetic (SPM) behavior for all NPs smaller than 20 nm. The observed blocking temperature, $T_{B}$ , gradually increases with NP size from about 25–150 K. In addition, the Verwey transition is observed with the emergence of a strong narrow peak at 125 K in the magnetization curves when larger NPs are present. Our data confirm the vanishing of the Verwey transition in smaller NPs. Magnetization loops indicate that the saturating field drastically decreases with NP size. While larger NPs show some coercivity ( $H_{c}$ ) up to 30 mT at 400 K, NPs smaller than 20 nm show no coercivity ( $H_{c} = 0$ ), confirming their pure SPM behavior at high temperature. Upon cooling below $T_{B}$ , some of the SPM NPs gradually show some coercivity, with $H_{c}$ reaching 45 mT at 5 K for the 10 nm NPs, indicating emergent interparticle couplings in the blocked state.

A long-range magnetic order in the topological insulator (Bi2Te3) achieved a great interest by the doping of magnetic elements on to Bi and Te-sites. The magnetic moments can be introduced by adding trivalent rare-earth elements such as Ce and I. In this report, Bi2Te3, Ce0.2Bi1.8Te3, and Ce0.2Bi1.8Te2.9I0.1 nanoparticle were synthesized by the novel low-temperature double solvent sol-gel technique. The co-doped nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), physical properties measurement system (PPMS), and vibrating sample measurement system (VSM). The VSM studies showed that the magnetization (M) of pure Bi2Te3 sample was successfully increased by adding iodine onto the Ce-doped sample (Ce0.2Bi1.8Te2.9I0.1). For in-depth analysis, PPMS results revealed that the as-synthesized samples exhibit paramagnetic nature which then exchange into antiferromagnetic behavior after substituting Ce I onto Bi2Te3, at a varying temperature range from 0 to 400 K. The density functional theory (DFT) was also performed to understand the exchange-biased phenomenon for as-synthesized samples. Moreover, the experimental results can predict that the magnetic samples synthesized by the novel double solvent sol-gel method can provide magnetic materials with large remnant magnetization compared with the pure Bi2Te3.

This article gives a review on some important experimental studies on the magnetization curves using different theoretical models. Applications of the law of approach to saturation magnetization and Langevin function to various kinds of magnetic materials belonging to different groups such as ferromagnetic, ferrimagnetic, antiferromagnetic, superparamagnetic materials at various experimental conditions, applied field ranges, and their dependencies on the applied field are collectively reviewed. Extraction of important magnetic parameters by fitting magnetization data with suitable models and their variation with composition, morphologies, size etc. along with the strategies adopted are also discussed. The purpose and outcomes of such studies along with future scope are also highlighted in this review.

YIG particles were obtained by Pechini method with a thermal annealing between 800 and 1200 °C. The formation of the cubic YIG phase was corroborated by means of X-ray diffraction (XRD), where YIG particles have crystallite size range between 107 and 303 nm. Magnetization dynamics were studied by means of magnetization hysteresis cycles, ferromagnetic resonance, and micromagnetic simulations. Different magnetic processes were determined as particle size function, and the magnetization dynamics can be explained by different contributions, such as single domain state, magnetic vortex state, and superparamagnetic behavior, besides considering their interactions. Graphical Abstract

Cerium hexaboride attracts attention of solid-state community for almost 50 years. Nowadays, this material is considered as a unique example of a system with orbital ordering resulting in formation of low-temperature magnetic phase with quadrupolar order, the so-called antiferroquadrupole phase. In crystal electric field 4f 1 state of Ce3+ splits into Γ7 doublet and Γ8 quartet, the latter is believed to be the ground state, as long as just Γ8 allows quadrupolar effects. An additional tool for studying rich physics of CeB6 appeared since the discovery in this material the ESR, which is specific to antiferroquadrupole (AFQ) phase and is missing in the paramagnetic phase. In the present review, we have brought together electron spin resonance and inelastic neutron scattering data, which allowed obtaining most detailed structure of the magnetic resonance modes in the AFQ phase in a wide-frequency range up to 0.6 THz. It is shown that apart paramagnetic resonance main mode with homogeneous precession of the magnetization, there are antiferromagnetic resonance modes as well, some of them existing in the AFQ phase. Analysis of the g factors demonstrates that available theories based on Γ8 ground state are facing difficulties with accounting experimental data, thus providing a challenge for developing of a theory correctly describing dynamic magnetic properties of this interesting material.

Development of new superparamagnetic materials with narrow size distribution is crucial for biomedical and environmental applications. Hence, we report the synthesis of narrow size distributed single grain MnFe2O4 nanoparticles of average particle size 9 nm by solvothermal reflux method. Synthesized compound crystallized in face centered cubic spinel structure and is confirmed by X-ray diffraction profiles. Transmission electron micrograph shows narrow size distributed particles with an average particle size of 9 nm and is equal to crystallite diameter estimated from Scherrer equation. The spinel crystal structure is further confirmed by electron diffraction profiles, Fourier transformed infrared spectrum, and Raman spectrum at room temperature. Magnetic properties of the sample show superparamagnetic nature at room temperature with moderate saturated magnetization of 56.4 emug−1. Magnetic heating properties of nanoparticles dispersion show the attainment of hyperthermia temperature (43 °C) in a short span of time of 1.6 min for 2 mg/mL and 2.6 min for 1 mg/mL concentrations. Estimated specific heat generation rate or specific power absorption rate, from temporal temperature plots, is 145.78 Wg−1 and is useful for magnetic hyperthermia application in cancer therapy. Photocatalysis properties of sample show 96% of rhodamine B dye degradation in little less than 6 h under UV light irradiation and are useful for photocatalytic applications in wastewater treatment in industries.

Pure SnO2, Sn0.94Co0.06O2, Sn0.91Co0.06Ag0.03O2, and Sn0.88Co0.06Ag0.06O2 compounds were synthesized by the solid-state reaction method. The structural characterization of these compounds by recording X-ray diffraction patterns (XRD) and analyzing them using Rietveld refinement analysis shows that these materials are in single-phase tetragonal rutile structure with typical lattice constant of a = b = 4.7385 A and c = 3.1871 A for SnO2 compound. SEM images show the formation of homogenous nanometer range spherical particles. Temperature variation of magnetization (M-T) measurements show a typical diamagnetic behavior in parent compound, while ferromagnetic (FM) to paramagnetic transition is observed in Sn0.94Co0.06O2 compound with a Curie temperature of 232.5 K. The (Co-Ag) co-doped SnO2 compounds undergo double ferromagnetic transitions. These compounds exhibit first FM transition below 620 K and another FM transition at 1108 K and 1052 K, respectively for Sn0.91Co0.06Ag0.03O2 and Sn0.88Co0.06Ag0.06O2 compounds. The measurement of magnetic hysteresis (M-H) curves at room temperature indicates the increase in coercivity and saturation magnetization values with the increase of (Co-Ag) co-doping concentration. The observed ferromagnetism was discussed based on the exchange interaction between Co2+ and Co3+ ions via oxygen vacancies.

The relationship between electrical and magnetic properties of manganites has been traced through the analysis of dependence of La0.47Eu0.2Pb0.33MnO3 (LEPMO) and La0.47Y0.2Pb0.33MnO3 (LYPMO) resistivity on temperature. The dependence of electrical resistivity on temperature shows a metal–semiconductor transition at TM-Sc and a decrease in TM-sc with Eu and Y substitution. The critical property of both systems around second order transition was investigated using Fisher–Langer relation and Suezaki–Mori method. The obtained exponents values from resistivity were so close to those predicted by the 3D-Ising model. These results and the analysis of the critical exponents from magnetization measurements were in good agreement. For low temperatures (T TM-Sc, for the two samples, the mechanism of electrical conduction is governed by the thermal activation model defined by $$\rho = \rho_{0} T\exp (E_{\text{a}} /k_{\text{B}} T)$$ . In order to understand the transport mechanism in the whole temperature range, the phenomenological percolation model, based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, was used in fitting the electrical resistivity. Therefore, it was found that the estimated values of the resistivity are in good agreement with experimental data. Magnetoresistance study showed a peak that has a great value around the transition temperature (TM-Sc).

In this work, the structural and magnetic transitions of Heusler alloy Ni50Mn34In14Ga2 have been carefully studied through measurements of heat flow and magnetization under DC and AC magnetic fields. This alloy undergoes the transition sequence of spin-glassy martensite (SPM) → ferromagnetic austenite (FA) → paramagnetic austenite at ∼225 and ∼305 K, respectively, during heating. Splitting of zero-field-cooling (ZFC)/field-cooling (FC) curves in martensite is caused by the slowdown dynamics of spin glass as evidenced by frequency dispersion and aging effects. The development of a spin-glass state is believed to be the result of strain relaxation and interaction of ferroelastic twin walls in the martensite. The magnetocaloric effect (MCE) at the SPM-FA transition was then measured using indirect, quasi-direct, and direct methods. The MCE magnitudes are controlled by the entropy changes associated with the first-order martensite transition and magnetic ordering of austenite under the magnetic field. The existence of a spin-glass state in martensite can also improve the reversibility of the magnetostructural transitions, which is beneficial for the improvement of the reversibility of associated MCE. These results provide an in-depth understanding of the transitions and magnetic properties of the Ni-Mn Heusler alloys and suggest that the MCE at the first-order magnetostructural transitions estimated solely using indirect methods may need some revision.

The influence of light exposure on the magneto-optical Kerr effect in the ferromagnetic semiconductor europium sulfide EuS has been studied. It has been experimentally established that when a sample is exposed to the light with a photon energy greater than the band gap, photoinduced magnetization occurs, which is associated with the formation of magnetic polarons with a large magnetic moment of about 3000 μB. The polarons are excited in a narrow temperature range of 12–18 K and form a superparamagnetic ensemble with an average polaron lifetime of 13 μs. A method for observing photo-induced magnetization using optical pump-probe technique has been described.

Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures. The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties. When the substrate temperature increases from room temperature to 400 °C, Co particles gradually grow, and the degree of Co oxidation significantly decreases. Consequently, the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400 °C. At a high substrate temperature, conductive pathways form among some of the clustered Co particles. Thus, resistivity rapidly declines from 1600 to 76 μΩ·m. The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76 μΩ·m. These results reveal that the obtained nanocomposite films have low Co oxidation, high magnetization and magnetoresistance at room temperature.

Nano-magnetic ferrites with composition Mg1−xZnxFe2O4 (x = 0.3, 0.4, 0.5, 0.6, and 0.7) have been prepared by coprecipitation method. X-ray diffraction (XRD) studies showed that the lattice parameter was found to increase from 8.402 to 8.424 Å with Zn2+ ion content from 0.3 to 0.7. Fourier transform infrared (FTIR) spectra revealed two prominent peaks corresponding to tetrahedral and octahedral at around 560 and 430 cm−1 respectively that confirmed the spinel phase of the samples. Transmission electron microscopy (TEM) images showed that the particle size was noted to increase from 18 to 24 nm with an increase in Zn content from x = 0.3 to 0.7. The magnetic properties were studied by vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) which ascertained the superparamagnetic behavior of the samples and contribution of superexchange interactions. The maximum magnetization was found to vary from 23.80 to 32.78 emu/g that increased till x = 0.5 and decreased thereafter. Further, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and substantiate their oxidation states.

With the aim to produce a material with magnetic and semiconductor properties, a lanthanide bismuth-ferrite type material is proposed in this work. Polycrystalline samples of Dy2Bi2Fe4O12 were produced following the standard solid-state reaction method. Structural characterization through the X-ray diffraction technique evidences that the synthesized ceramic crystallizes in a perovskite-like orthorhombic structure, belonging to the Pnma (#62) space group. Scanning electron microscopy images revealed the granular nature of the samples with mean grain sizes of nanometric order. X-ray energy dispersion spectra allowed establishing that in the samples there are no elements different from those expected in the stoichiometric proportions suggested by the chemical formula of the compound. Studies of electrical behavior were carried out using I–V curves and electrical permittivity as a function of frequency and temperature, which show the diode varistor feature of this material with a marked Maxwell–Wagner-type trend. The semiconductor band gap was determined from the analysis of diffuse reflectance spectra that reveal Eg = 1.88 eV. Temperature-dependent magnetization curves for applied fields of 1.0, 5.0 and 10 kOe showed the behavior expected for ferromagnetic type materials, with strong evidence of magnetic frustration causing irreversibility in curves obtained from Zero Field Cooling and Field Cooled measurement procedures. The magnetization hysteresis curves at temperatures of 50, 200 and 300 K exhibit a ferromagnetic response with evidence of superparamagnetic effects due to the significant presence of nano-sized ferromagnetic grains. Based on the obtained results, it can be affirmed that the material behaves like a soft ferrimagnetic semiconductor with low coercive field (between 500 Oe and 700 Oe) and remnant magnetization (between 2.15 × 10−4 emu/g and 3.25 × 10−4 emu/g) that would have eventual technological implications in the spintronic industry.

Superparamagnetic iron oxide nanoparticles (SPIONs) are emerging nanomaterials, in part due to their superparamagnetic property. At room temperature, they can be readily magnetized under the influence of an external magnetic field and yet return to an apparently nonmagnetic state in its absence, with closed (no hysteresis) magnetization curves resulting in zero magnetic remanence and coercivity. Their high surface to volume ratio due to the nanometer length scale and subsequent high surface area enables them to be used in a range of applications that includes targeted drug delivery, magnetic contrasting agents in MRI scans for medical diagnosis, and in localized heating induced by an alternating magnetic field (AMF) for targeted therapy with minimum side effects. In this chapter, we systematically introduce the concept of magnetic nanomaterials, superparamagnetic materials such as SPIONs, various syntheses routes, various core-shell SPIONs, surface functionalization of core-shell SPIONs, main characterization techniques, and application of SPIONs in medical diagnosis and therapy. We have also summarized the current state of commercially available SPIONs and their applications in nanomedicine including information of clinical trials. Finally, we have provided an overview of the potential theranostics application of SPIONs in various diseases.

In the field of nanoscale magnetocaloric materials, novel concepts like micro-refrigerators, thermal switches, microfluidic pumps, energy harvesting devices and biomedical applications have been proposed. However, reports on nanoscale (Mn,Fe)2(P,Si)-based materials, which are one of the most promising bulk materials for solid-state magnetic refrigeration, are rare. In this study we have synthesized (Mn,Fe)2(P,Si)-based nanoparticles, and systematically investigated the influence of crystallite size and microstructure on the giant magnetocaloric effect. The results show that the decreased saturation magnetization (Ms) is mainly attributed to the increased concentration of an atomically disordered shell, and with a decreased particle size, both the thermal hysteresis and Tc are reduced. In addition, we determined an optimal temperature window for annealing after synthesis of 300–600 °C and found that gaseous nitriding can enhance Ms from 120 to 148 Am2kg−1 and the magnetic entropy change (ΔSm) from 0.8 to 1.2 Jkg−1K−1 in a field change of Δμ0H = 1 T. This improvement can be attributed to the synergetic effect of annealing and nitration, which effectively removes part of the defects inside the particles. The produced superparamagnetic particles have been probed by high-resolution transmission electron microscopy, Mössbauer spectra and magnetic measurements. Our results provide important insight into the performance of giant magnetocaloric materials at the nanoscale.

Precise control of the crystal field and symmetry around the paramagnetic spin centre has recently facilitated the engineering of high-temperature single-ion magnets (SIMs), the smallest possible units for future spin-based devices. In the present work, we report a series of air-stable seven coordinate Dy(III) SIMs {[L 2 Dy(H 2 O) 5 ][X] 3 ·L 2 · n (H 2 O), n = 0, X = Cl ( 1 ), n = 1, X = Br ( 2 ), I ( 3 )} possessing pseudo- D 5h symmetry with high energy barrier ( U eff ) and blocking temperature ( T B ). While the strong axial coordination from t BuPO(NH i Pr) 2 ( L ), increases the overall anisotropy of the system, the presence of high symmetry significantly quenches quantum tunnelling of magnetization. The energy barrier ( U eff ) and the blocking temperature ( T B ) decrease in the order 3 > 2 > 1 with the change of anions from larger iodide to smaller strongly hydrogen-bonded chloride in the secondary coordination sphere, albeit the local coordination geometry and the symmetry around the Dy(III) display only slight deviations. Ab initio CASSCF/RASSI-SO/SINGLE_ANISO calculations further provide deeper insights into the dynamics of magnetic relaxation in addition to the role of the secondary coordination sphere in modulating the anisotropy of the D 5h systems, using diverse models. Thus, in addition to the importance of the crystal field and the symmetry to obtain high-temperature SIMs, this study also probes the significance of the secondary coordination sphere that can be tailored to accomplish novel SIMs.

Ferromagnetic (FM) electrocatalysts have been demonstrated to reduce the kinetic barrier of oxygen evolution reaction (OER) by spin-dependent kinetics and thus enhance the efficiency fundamentally. Accordingly, FM two-dimensional (2D) materials with unique physicochemical properties are expected to be promising oxygen-evolution catalysts; however, related research is yet to be reported due to their air-instabilities and low Curie temperatures (TC). Here, based on the synthesis of 2D air-stable FM Cr2Te3 nanosheets with a low TC around 200 K, room-temperature ferromagnetism is achieved in Cr2Te3 by proximity to an antiferromagnetic (AFM) CrOOH, demonstrating the accomplishment of long-ranged FM ordering in Cr2Te3 because the magnetic proximity effect stems from paramagnetic (PM)/AFM heterostructure. Therefore, the OER performance can be permanently promoted (without applied magnetic field due to nonvolatile nature of spin) after magnetization. This work demonstrates that a representative PM/AFM 2D heterostructure, Cr2Te3/CrOOH, is expected to be a high-efficient magnetic heterostructure catalysts for oxygen-evolution.

To develop one-dimensional spintronic devices, we synthesize Gd-filled double-walled carbon nanotubes where the long spin-coherence time of a paramagnetic gadolinium (Gd3+) ion and the discrete phonon modes of a carbon nanotube can be combined. Here, we report Raman observation of spin–phonon coupling in the Gd-filled double-walled nanotubes by analyzing the low-temperature dependence of the dominant phonon modes (G-band). A G-band (w+G ext and w +G int) phonon frequency hardening is observed below a critical temperature of TC ∼ 110 K coinciding with the onset temperature of superparamagnetic behavior confirmed through magnetization studies. This anomalous behavior is ascribed to phonon renormalization induced by spin–phonon coupling interaction. The estimated spin–phonon coupling constant values are 12.2 and 5.0 cm−1 for G +ext and G +int phonon modes, respectively, analyzed by comparing the phonon frequency variation (Δw) to magnetization as a function of temperature. Realizing a spin–phonon coupling (three times higher than for other multiferroic compounds) interface and modulating it in a one-dimensional system have potential benefit when designing effective molecular qubits.

Superconductivity induced by a magnetic field near metamagnetism is a striking manifestation of magnetically-mediated superconducting pairing. After being observed in itinerant ferromagnets, this phenomenon was recently reported in the orthorhombic paramagnet UTe$_2$. Under a magnetic field applied along the hard magnetization axis b, superconductivity is reinforced on approaching metamagnetism at $\mu_0H_m$ = 35 T, but it abruptly disappears beyond $H_m$. On the contrary, field-induced superconductivity was reported beyond $\mu_0H_m$ = 40-50 T in a magnetic field tilted by $\simeq25-30\deg$ from b in the (b,c) plane. Here we explore the phase diagram of UTe2 under these two magnetic-field directions. Zero-resistance measurements permit to confirm unambiguously that superconductivity is established beyond Hm in the tilted-field direction. While superconductivity is locked exactly at fields either smaller (for a H || b), or larger (for H tilted by $\simeq27\deg$ from b to c), than Hm, the variations of the Fermi-liquid coefficient in the electrical resistivity and of the residual resistivity are surprisingly similar for the two field directions. The resemblance of the normal states for the two field directions puts constraints for theoretical models of superconductivity and implies that some subtle ingredients must be in play., Comment: 18 pages, 5 Figures, includes Supplementary Information (9 pages, 8 Figures)

Pr0.57Ca0.43MnO3 (PCMO) & Pr0.57Ca0.43Mn0.98Ga0.02O3 (PCMGO) manganites are synthesized by sol gel technique. Structural characterization was done through XRD, SEM, TEM, FTIR and EDAX analysis. Magnetization measurements were carried out through Vibration Sample Magnetometer (VSM). Field cooled (FC) and Zero field cooled (ZFC) magnetization of both the nano particles with respect to temperature were studied and compared. Pr0.57Ca0.43MnO3(PCMOB) bulk sample is charge ordered(CO) at temperature 240K and shows antiferromagnetic (AFM) ordering peak at temperature TN=170K. We recorded the Ferromagnetic (FM) transition in 2% Ga doped Pr0.57Ca0.43Mn0.98Ga0.02O3 (PCMGOB) bulk sample but CO peak remains unaltered. Interestingly disappearance of CO and emergence of FM phase is found in both PCMO and PCMGO nano particles. FM transition is further confirmed by magnetization hysteresis studies. Both the nano particles exhibit Superparamagnetic behavior with blocking temperature at TB=35 K. The possible reasons for the observed results are discussed.

All substances exert magnetic properties in some extent when placed in an external magnetic field. Magnetic susceptibility represents a measure of the magnitude of magnetization of a certain substance when the external magnetic field is applied. Depending on the tendency to be repelled or attracted by the magnetic field and in the latter case on the magnitude of this effect, materials can be classified as diamagnetic or paramagnetic, superparamagnetic and ferromagnetic, respectively. Knowledge of type and extent of susceptibility of common endogenous and exogenous substances and how their magnetic properties affect the conventional sequences used in magnetic resonance imaging (MRI) can help recognize them and exalt or minimize their presence in the acquired images, so as to improve diagnosis in a wide variety of benign and malignant diseases. Furthermore, in the context of diamagnetic susceptibility, chemical shift imaging enables to assess the intra-voxel ratio between water and fat content, analyzing the tissue composition of various organs and allowing a precise fat quantification. The following article reviews the fundamental physical principles of magnetic susceptibility and examines the magnetic properties of the principal endogenous and exogenous substances of interest in MRI, providing potential through representative cases for improved diagnosis in daily clinical routine.

It is crucial to investigate the slow relaxation mechanisms of binuclear Er III -based single-molecule magnets (SMMs) and explore the strategies for optimizing their magnetic properties. Herein, a doped compound, [Y 1.75 Er 0.25 (thd) 4 Pc]·2C 6 H 6 ( YEr·2C 6 H 6 , Hthd = 2,2,6,6-tetramethylheptanedione, H 2 Pc = phthalocyanine), was synthesized by doping paramagnetic erbium(III) compound Er 2 ·2C 6 H 6 in a diamagnetic yttrium(III) matrix Y 2 ·2C 6 H 6 . The doping effect was studied using SQUID magnetization measurements. The results suggest that magnetic-site dilution improves the magnetic property from a fast relaxation of pure Er III compound to a typical SMM relaxation process of doped sample. In this binuclear system, the dominant single-ion relaxation is entangled with the neighboring Er III ion through the intramolecular Er III ···Er III interaction, which plays the important role in suppressing the quantum tunneling of the magnetization (QTM) process. Furthermore, the influence of lattice solvents on single-ion relaxation was studied. By releasing the benzene molecules, compound YEr·2C 6 H 6 can be successfully transformed to a desolvated sample YEr accompanied by structural alteration and improved SMM performance.

The influence of cobalt doping on bismuth nickelate (Bi12NiO19) synthesized by sol–gel method has been investigated. The X-ray powder diffraction analysis proves that bismuth nickelate possesses cubic perovskite structure, and the same is retained even after Co doping. The average crystallite sizes were found to be in the range of 42–60 nm as estimated by Scherrer’s formula. The morphology of the samples analyzed by scanning electron microscopy reveals irregular-shaped structures of the samples. However, incorporation of Co has led to a significant morphological transformation. The dielectric properties were found to be consistent with the Koop’s phenomenological theory. Nyquist plots exhibit only one incomplete and distorted semicircle for all the samples specifying that the relaxation process deviates from the ideal Debye-type behavior. Magnetization measurements carried out using vibrating sample magnetometry (VSM) revealed paramagnetic behavior of the investigated samples. The results obtained from the impedance analysis give a true picture of the electrical behavior of the sample. The cobalt-doped bismuth nickelate ceramics have good prospects in scientific and industrial applications in the fields of sensors and memory devices.

Perovskite manganit merupakan salah satu rekayasa material yang dapat menghasilkan perubahan fenomena fisika. Telah berhasil dibuat material berbasis perovskite manganit Nd0,6Sr0,4MnO3 menggunakan metode sol-gel¬ dan dikompositkan dengan ZnO (Nd0,6Sr0,4MnO3)1-x/(ZnO)x (x = 0; 0,3; 0,5; 0,7). Hasil pengujian X-Ray Diffraction menunjukkan sampel Nd0,6Sr0,4MnO3 berstruktur tunggal ortorombik dan sampel ZnO pada (Nd0,6Sr0,4MnO3)0,5/(ZnO)0,5 berstruktur heksagonal tunggal. Hasil pengujian Field Emission Scanning Electron Microscope menunjukkan sampel telah homogen dengan rata-rata ukuran butir 0,188 μm. Hasil pengujian Vibrating Sample Magnetometer menunjukkan sampel (Nd0,6Sr0,4MnO3)0,5/(ZnO)0,5 bersifat paramagnetik dan mengalami penurunan sifat magnetik juga suseptibilitas seiring dengan penambahan konsentrasi material ZnO. AbstractPerovskite manganite is one of the manipulation materials that can produce changes in physical phenomena. Perovskite material Nd0,6Sr0,4MnO3 has been made with the sol-gel method and then composites with ZnO (Nd0.6Sr0.4MnO3)1-x/(ZnO)x (x = 0; 0.3; 0.5, 0, 7). The results of the X-Ray Diffraction characterization test showed samples of Nd0,6Sr0,4MnO3 and ZnO each with a single orthorhombic phase with a Pnma space group and a single hexagonal with a P63mc space group. The results of the Field Emission Scanning Electron Microscope characterization test showed that the samples were homogeneous with an average grain size of 0,188 μm. Vibrating Sample Magnetometer characterization test results show composite material (Nd0,6Sr0,4MnO3)1-x/(ZnO)x are paramagnetic and the increasing composition of ZnO material decreases the magnetization and susceptibility value of sample

Nickel/nickel oxide-carbon magnetic fibers were prepared by Solution Blow Spinning (SBS) of polyvinyl alcohol (PVA) and Ni-nitrate. As-spun fibers with relative Ni nitrate/PVA concentrations of 30 wt% and 60 wt% were calcined at 550 °C in argon flux. The samples characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and DC magnetic measurements. TEM images show a carbon matrix containing sphere-like nanoparticles with diameters in the range of 4–45 nm. The magnetic assessment shows the presence of superparamagnetic small particles with blocking temperatures between 14 and 22 K, and large particles that are thermally blocked at 300 K. The low magnetization signal, with saturation magnetization in the range of 7–10 emu/g, is due to dead magnetic layers at the surface of nanoparticles.

Based on the effective mass approximation, the magnetic and thermal properties of parabolic GaAs quantum dot have been investigated in the presence of Rashba Spin-Orbit interaction (RSOI), donor impurity and applied magnetic and electric fields. The exact diagonalization method has been used to solve the Hamiltonian of an electron confined in a quantum dot (QD) and obtain the eigenenergies and the binding energy of the donor impurity as a function of various QD physical parameters. We have shown the dependence of the average statistical energy, magnetization, magnetic susceptibility and heat capacity of the donor impurity in the QD on: the Rashba interaction parameter, the magnetic and electric fields, confining frequency, and temperature. The results reveal that these parameters can tune the magnetic properties of the GaAs quantum dot and flip the sign of magnetic susceptibility from negative (diamagnetic) to positive (paramagnetic) type material.

We have investigated the structural and magnetic properties of (Zn,Fe)Te:N thin films grown under Zn-rich condition with Fe composition fixed at 1.4% and N concentrations varying in the range [N] = 1.8 × 1018–5.1 × 1019 cm−3. Structural analysis by x-ray diffraction (XRD) detects some additional extrinsic diffraction peaks possibly from Fe-N compounds in the N-doped film with [N] = 5.1 × 1019 cm−3 only. Accordingly, x-ray absorption fine structure (XAFS) analysis reveals the shifting of Fe atoms from substitutional position for N-doped films with high N concentrations, [N] ≥ 1.8 × 1019 cm−3, whereas N-doped films with intermediate N concentrations [N] ≤ 4.3 × 1018 cm−3 are composed of pure diluted phase with substitutional Fe atoms in the valence state deviating from Fe2+. Magnetization measurement using SQUID confirms drastic change of magnetic properties; the linear dependence of magnetization on magnetic field, typical of van Vleck-type paramagnetism in the film without N-doping changes into room temperature ferromagnetic behaviors with hysteretic magnetization curves for N-doped films. The observed weak room temperature ferromagnetic behavior of the N-doped films with [N] ≤ 4.3 × 1018 cm−3 may reflect the deviation of substitutional Fe valence state from Fe2+ to Fe2+/3+ mixed states. On the other hand, the robust room temperature ferromagnetic behavior exhibited by N-doped films with [N] ≥ 1.8 × 1019 cm−3 may originate from precipitates of Fe-N compounds with Fe being in Fe2+/3+ or other valence state.

Recently Ni–Co mixed oxide nanoparticles have received tremendous attention for their application potential in electrochemical devices, biosensing, and biomedical treatments. However, the biomedica...

The ground states phase diagrams and magnetizations properties of ferrimagnetic model on decorated hexagonal nanolattice have been studied via Monte Carlo simulations. The shape of the phase diagrams depends of the values of the magnetic parameters given in the Hamiltonian. The phase diagrams show some key features: coexistence between regions, points where two, three, four and five and states can coexist. This richness of the ground state phase diagrams can serve as a guide for exploring interesting regions of the model’s finite temperature phase diagrams. The transition temperatures have been deduced for different values of exchange interactions between the atoms of spins moments(S). The effect of crystal field and exchange interactions on magnetization has been investigated. The magnetic coercive field and remanent magnetization are obtained for different parameters such as: exchange couplings and temperatures values. The superparamagnetic behavior has been found at the transition temperature.

In this work, the magnetic and magnetocaloric properties of (La0.7Sm0.3)0.67Ba0.33MnO3 manganite produced by sol–gel method were investigated by magnetization and direct-temperature change measurements. As the temperature decreases in M(T) measurements, the sample shows the transition from paramagnetic to ferromagnetic state at 160 K, which is the magnetic phase transition temperature where magnetization suddenly drops. The maximum magnetic entropy change value from M(H) measurements in the transition region is determined as 2.12 Jkg−1 K−1 under 4.8 T magnetic field. It was found that the material had a second-order transition due to the positive slope of the Arrott plots, and this behavior was confirmed by the universal curve obtained by the normalized magnetic entropy change curves versus the rescaled temperature axis. ΔTad of the sample was measured with the adiabatic magneto-calorimetry system directly and the maximum value of ΔTad was measured as 0.72 K under 3 T magnetic field change.

MnZnFe2O4 ferrite was successfully synthesized using metallic chlorides and polyvinylpyrolidone, by Co-precipitate method. Deferent concentrations of PVP (0.1, 0.3, 0.5, 0.7, and 0.9) wt%, were used as capping agent to stabilize the particles and prevent them from agglomeration. The PVP content had a vital influence on enhancing the properties of the ferrite nanoparticles. From X-ray data the degree of crystallinity and the Lattice constants (a) of the nanoparticles increased from (8.92 nm) and (8.344 A) to (19.94 nm) and (8.395 A) respectively with increasing PVP concentrations. The morphology and average particle size of the MnZn ferrite nanoparticles were evaluated by scanning electron microscopy (SEM), the values were in a good agreement with the XRD results. Fourier transform infrared spectroscopy (FT-IR) confirmed the cubic structure with octahedral and tetrahedral, also indicated the formation of bond between PVP and surface of metallic hydroxide of ferrite nanoparticles. Vibrating sample magnetometer (VSM) analysis was performed for all samples at room temperature, results showed that the specimens exhibited a paramagnetic behavior in the absence of PVP while in the presence of PVP they have super paramagnetic characteristics. The values of saturation magnetization (Ms) (1.78–17.67 emu/g), remnant magnetization (Mr) (0.0022–0.0696 emu/g) also increased with increasing pvp concentration. Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites were used it alone or as a combination therapy with NIR laser, and alternating magnetic field (AMF) as anti-proliferative agent against breast cancer cell lines AMJ-13, MCF-7,and ovarian cancer cell line SKOV-3 as well as against normal cell line HBL. While, its capability to induce apoptosis was detected using different techniques which is acridine orange/ethidium bromide (AO/EtBr) staining and mitochondrial membrane potential (MMP), and flow cytometry assay membrane potential (MMP). q-PCR was used to investigate the changes in the expression of P53 gene. The influence of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites in viability of breast and ovarian cancer cells alone or when they used as a combination therapy with laser photo-thermal therapy and alternating magnetic field (AMF) was also tested using MTT assay. Our results in the present study demonstrated that the inhibition activity of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites against treated cancer cell lines increased when Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites used with NIR laser, while highly increased cytotoxic activities were observed after exposure of Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites to induction heating with AMF. Treated cancer cells with polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites significantly increased ROS synthesis, with subsequent reduction of the MMP. The results of the current study show that tested compounds suppressed cancers cells’ proliferation and has a growth inhibitory effect on different cancer cells, resulting in apoptosis as a novel pathway that involves mitochondrial damage mechanism via activated P53. Taken together the present data suggest that the Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites could be promising therapy protocol for cancer cells.

Ternary FeCrNi thin films were sputtered on polyimide substrates from the source (austenitic AISI 304 stainless steel) under the substrate rotation speeds of 0, 15, 30 and 45 rpm, respectively. The films with 50 nm thickness were sputtered at 0.9 nm/s. To the elemental measurements, while the Fe content slightly varied, Ni increased and Cr content decreased as the rotation speed increased. And, all films have a single crystal of (110) peak at the angle of 2θ ≈ 44.7° which is body-centred tetragonal (bct) martensitic α′-phase. Also, the peak intensity of (110) slightly varied as a result of changes of FeCrNi martensitic alloy contents in the films. Moreover, increasing substrate rotation speed resulted in a decrease in grain size. The morphologic analysis by a scanning electron microscope and an atomic force microscopy displayed a more homogenous structure and the decrease of film roughness parameters with increasing of rotation speed, respectively. For magnetic measurements, the saturation magnetisation, Ms increased from 995 to 1172 emu/cm3 and the coercivity, Hc decreased from 88 to 52 Oe with the increase of rotation speed. In the films, the increases of the martensitic structure formations and the decrease of the grain size were observed to have probably caused the increase of the MS values and the decrease of the HC values, respectively. As observed from the XRD results, ferromagnetic behaviour of the films may be due to the martensitic phase since austenitic phase has a weak paramagnetic behaviour as a source material at room temperature. From the parallel and perpendicular hysteresis loops, the films can also be obtained to have uniaxial in-plane anisotropy with increasing rotation speed. It is seen that the film properties can be easily varied by changing rotation speed for potentially new device applications such as spintronics, magnetic hetero-structures, magnetic separators, etc. on flexible substrates.

In this study, iron oxide (γFe2O3) nanoparticles synthesized via hydrothermal route and doxorubicin (Dox) were successfully encapsulated into natural almond gum hydrocolloids via antisolvent precipitation technique. Cubic γFe2O3 crystal structure of the synthesized iron oxide nanoparticles were confirmed using X-ray diffraction and X-ray photoelectron spectroscopy. The refinement of XRD and elemental analysis revealed oxygen vacancies, which is also indicated by an increased magnetization comparable to bulk γFe2O3. Magnetization studies revealed the superparamagnetic nature of IO and IODPC nanoparticles. The particles were characterized for its morphology (TEM and FESEM), size (FESEM, DLS), surface charge (DLS) and MRI (proton relaxation). The heating ability of the IO and IODPC nanoparticles was studied and their specific absorption rate was found to be 83.06 W/g and 154.37 W/g respectively. The entrapment efficiency of the IODPC nanoparticles was found to be 88.29%. The drug release studies revealed that IODPC nanoparticles were more responsive towards acidic pH and their release follows Higuchi diffusion kinetics. In-vitro uptake and in-vitro cell viability studies were performed for IODPC nanoparticles using HeLA cell lines.

Magnetization enhancement is observed in the bi-magnetic systems including paramagnetic (PM)/antiferromagnetic (AFM), AFM/AFM, and ferromagnetic (FM)/AFM composites systems, and attributed to the effects of oxidation states of metallic ions on the interface exchange-coupling. With respect to the FM/FM system, in this study, the enhanced magnetization in hard CoFe2O4 (CFO)/soft La0.7Sr0.3MnO3 (LSMO) composites with different mass ratios of LSMO (Rs) was observed for the first time. The values of saturation magnetization (Ms) of CFO and LSMO at 10 K were found to be 111 and 113 emu/g, respectively. For the CFO/LSMO composites, Ms was below 111 emu/g for Rs ≤ 15% because the antiferromagnetically coupled CFO/LSMO system maintains the super-spin glass (SSG) state with the moment of CFO particles being randomly oriented. However, Ms increases to 133 and 127 emu/g for Rs = 18 and 21%, respectively, because the higher content of LSMO separates the CFO particles and destroys the SSG state, thus enabling the moment of CFO particles to rotate easily and align with the external magnetic field. Mechanism for the magnetization enhancement reported herein is different from the interface exchange-coupling mechanism, which enriches the understanding of the magnetization reversal in bi-magnetic systems and provides the experimental reference for the applications of bi-magnetic materials.

In this study, solid solutions of (1-x)BaTiO3-xBiMnO3 have been synthesized by an aqueous sol-gel method. It was determined that single-phase compounds can be obtained up to x = 0.6 and with further increase in percentage of BiMnO3 component additional crystal phases were detected. Perovskite crystal structure was determined for all synthesized compounds regardless of chemical composition. Raman spectra of synthesized solid solutions showed gradual change of the shape with an increase of BiMnO3 fraction. It was demonstrated that partial substitution of BaTiO3 by BiMnO3 led to the drastic growth of grains of the end products. Magnetization measurements showed that all BiMnO3-containing samples are characterized by paramagnetic behavior. Clear correlation between magnetization values and composition of the materials was observed, magnetization values increased with increasing of BiMnO3 content in solid solutions.

Adsorption studies were carried out to determine the behavior of three carbonaceous adsorbents with different magnetic orderings (ferromagnetic, paramagnetic, and diamagnetic) and the effect of an external magnetic field on the adsorption of a cation (lead, Pb2+) and an anion (fluoride, F–). Two different static magnetic field intensities were used to analyze the sensitivity of the adsorption system as a function of the applied magnetic field, based on computational simulations, with the aim of determining the degree of magnetization of each system and the distribution of the flow density generated by each magnetic field application system. The results of the adsorption studies for the removal of Pb2+ showed a correlation between the adsorption capacities and the magnetic ordering of the adsorbent material. Particularly, the activated carbon of bituminous coal (ferromagnetic) showed an increase of 15%, whereas bone char (paramagnetic) showed an increase of 6%. On the other hand, this behavior was not observed in the studies for the removal of fluoride.

Superparamagnetic cobalt ferrite nanoparticles (CoFe2O4) possess favourite advantages for theranostic applications. Most of previous studies reported that CoFe2O4 magnetic nanoparticles (MNPs) are suitable candidates for induction of hyperthermia and transfection agents for drug delivery. The present study synthesized and investigated the potential use of CoFe2O4 as a contrast agent in magnetic resonance imaging (MRI) by using a conventional MRI system. The CoFe2O4 were synthesized using co-precipitation method and characterized by TEM, XRD, FTIR, EDX and VSM techniques. Relaxivities r 1 and r 2 of CoFe2O4 were then calculated using a 1.5 Tesla clinical magnetic field. The cytotoxicity of CoFe2O4 was evaluated by the MTT assay. Finally, the optimal concentrations of MNPs for MRI uses were calculated through the analysis of T 2 weighted imaging cell phantoms. The superparamagnetic CoFe2O4 NPs with an average stable size of 10.45 nm were synthesized. Relaxivity r 1,2 calculations resulted in suitable r 2 and r 2/ r 1 with values of 58.6 and 51 that confirmed the size dependency on relaxivity values. The optimal concentration of MNPs for MR image acquisition was calculated as 0.154 mM. Conclusion: CoFe2O4 synthesized in this study could be considered as a suitable T 2 weighted contrast agent because of its high r 2/r 1 value.

In this work, a comparative study of the synthesis and magnetic properties of Fe3O4 nanoparticles obtained by the co-precipitation and hydrothermal methods with the adding of the sucrose as a chelating agent is reported. The analysis of X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) show that particles are spherical-like with an average particle size ranging of 3 ≤ d ≤ 10 nm. Magnetization measurements as a function of an applied magnetic filed and temperature are consistent with a superparamagnetic behavior with small T B values. The analysis of the M v s H loops measured at T = 2 K and Zero-Field-Cooled and Field-Cooled ( Z F C − F C ) curves allows us to estimate the average diameter of Fe3O4 nanoparticles. These results are in good agreement with those obtained through XRD data (by using Scherrer equation and Williamson-Hall plot) and slightly smaller than those estimated using TEM images. Finally, Z F C − F C data are also used to evaluate the effective anisotropy constants, which are similar to those values found in literature considering the average sizes values estimated by different techniques.

The new borophosphates were successfully synthesized by solution combustion synthesis assisted with glycine. The obtained materials were systematically characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction, UV–visible spectroscopy, thermogravimetric analysis, scanning electron microscopy, Brauner-Emmett-Teller surface area, and magnetometry. The Rietveld refinements indicated that Fe2B(PO4)3 is a hexagonal, space group P63/m with a = b = 8.029 and c = 7.408. As Cr substitutes the Fe atoms, there is a significant decrease in the lattice parameters. When all Fe atoms are replaced by Cr, Cr2B(PO4)3 is formed and the structure turns out to be a trigonal, space group P3 with a = b = 7.950 and c = 7.360. The materials are thermally stable and demonstrate paramagnetic behavior at room temperature. The magnetization increases as the iron content increases because of the high magnetic moment of the iron ion. Temperature-dependent magnetic measurements reveal that Fe2B(PO4)3 has a Neel transition at 30 K and the Neel temperature decreases with Cr substitution.

A detailed study has been carried out of the static and dynamic magnetic properties of ferrimagnetic spinel MgFe1.2Ga0.8O4 nanoparticles (NPs), including the measurements of low-field dc-magnetization M(T) under zero-field-cooled (ZFC) and field-cooled (FC) conditions and ac-susceptibility χac(T) at different frequencies (f) and amplitudes of the ac-field (Hac). Below, a Curie temperature (TC), a clear magnetic irreversibility (MZFC(T) ≠ MFC(T)), as well as a broad peak in both MZFC(T)–MFC(T) magnetizations have been observed. At T ≪ TC, the two distinct, frequency-dependent peaks at Tp1 ≈ 9 K and Tp2 ≈ 14 K in the imaginary part of the ac-susceptibility χac''(T) have been found. Their positions have been consistent with those of the anomalies detected on the temperature dependence of the magnetic contribution to the heat capacity Cmag(T), and a sharp decrease of the MZFC(T) magnetization near ≈ 10–20 K. It was revealed that the fitting of the frequency dependence of the peaks’ positions (Tp1(f) and Tp2(f)) in the imaginary part of ac-susceptibility χac''(T) using the Neel-Arrhenius law yields unphysical values of the relaxation time (τ0) and, therefore, these results ruled out a possibility of an existence of superparamagnetic (SPM) clusters in the system. On the other hand, the Tp1(f) and Tp2(f) dependences followed both the Vogel-Fulcher law and the power law. These observations indicate that, a complex magnetic state in MgFe1.2Ga0.8O4, realized in the low temperature region, may likely be related to a progressive freezing of magnetic clusters.