Variation Of Saturation Magnetization Research Articles

Multiferroic properties of NiFe2O4-Ba0.7Ca0.3TiO3 nanocomposites

In this report, we present results on the multiferroic properties of four nanocomposite samples of NiFe2O4-Ba0.7Ca0.3TiO3 (NFO/BCTO), which were fabricated through combinations of high-energy ball milling, heat treatment, and spark plasma sintering techniques. Structural analyses revealed that these samples simultaneously contain two phases of nano-sized NiFe2O4 (NFO) and Ba0.7Ca0.3TiO3 (BCTO) crystals. The addition of NFO into the BCTO-host did not alter the crystal structure but significantly improved the multiferroic characteristics compared to pure BCTO. Furthermore, variations in saturation magnetization (M s) and coercivity (H c) were investigated as a function of temperature. The results showed that Ms increased gradually with the concentration of NFO. In terms of temperature dependence, M s(T) data deviated from the Bloch’s law with an exponent coefficient α changing in the range of 1.8–1.9, decreasing gradually as the NFO concentration increased. Meanwhile, H c decreased gradually as the NFO concentration increased and followed the Kneller’s law in terms of temperature dependence.

Structural properties controlled magnetisation of Ni/Al multilayers sputtered on flexible polymer substrate: Impact of Ni deposition rates

The goal of this work is to determine how the rate of Ni deposition rates affect the structural characteristics that regulate the magnetization of Ni/Al multilayer thin films sputtered on flexible acrylic acetate polymer substrates. The films with a 5[Ni(20 nm)/Al(10 nm)] structure were gradually sputtered as different Ni deposition rates in the total thickness of 150 nm. With an increase in the rate of Ni deposition, the Ni contents increased from 61.5% to 69.6%. And, X-ray diffraction analysis verified that the films featured a face-centered cubic structure with variable peak intensities. Also, the scanning electron microscopy surface morphology analyses revealed that variations in the film surfaces were a result of the deposition rates. For magnetic measurements, the differences in the structural analysis were observed to cause a notable variation in saturation magnetization, MS, and coercivity, HC values. Accordingly, MS values increased consistently between 359.0 and 389.7 emu cm−3, but HC values decreased from around 34–32 to 28 Oe with the increase in Ni deposition rate from 0.02 to 0.10 nm s−1. It is also observed that when the Ni layers are generated at very fast deposition rates, the Ni/Al multilayer films have a high MS/HC ratio, which is significant for magnetic sensors. It has been concluded that the magnetisation of Ni/Al multilayer thin films can be controlled by the structural properties adjusting the Ni deposition rate.

Preparation and analysis of Mn1-xZnxFe2O4 nanoparticles coated with chitosan for use as a heating agent and MRI contrast agent in biomedical applications

Nanoferrites, day by day become the center of attraction due to their acceptability as contrast agents due to their enhanced properties. Wet chemical coprecipitation was used to prepare Mn1-xZnxFe2O4 nanoparticles. In order to apply the material for biomedical applications, the nanoferrites were also coated with the biodegradable material chitosan. XRD spectra confirmed the spinel ferrite configuration. It also showed that the structure was face centered cubic. TEM and HRTEM images in both bright- and dark- fields were used to analyze the surface structure and particle size. The particle size was observed below 10 nm. From EDS analysis, the elemental composition of the as-dried and coated materials was determined. No impurity was observed in the material. Along with XRD, FTIR also confirmed the formation of bare and coated spinel ferrites. Two characteristic bands were observed for the material that is also the basic features of the ferrite material. Using an M−H diagram, the variation in saturation magnetization and coercivity as a function of zinc content in the coating was investigated in great depth. It was observed that the saturation magnetization vary a little for coating material. The polydispersity index (PDI) and hydrodynamic diameter of the chitosan-coated solution were determined at 2 mg/ml and 4 mg/ml concentrations. It was seen that Mn0.8Zn0.2Fe2O4 and Mn0.6Zn0.4Fe2O4 at both concentrations were exhibit PDI value within the permissible range. It was discovered through an in-vitro cytotoxicity test on HeLa cancer cells that all of the coated samples were nontoxic to use. Relaxivity values were calculated using MRI images. The relaxivities progressively decreased in value as the zinc ions rose. TOF tests were used to examine the effect of the contrast agent. The samples’ heating profiles were examined to determine whether coated nanoferrites were suitable for use in applications involving hyperthermia. It has been noted that the Mn0.6Zn0.4Fe2O4 sample is appropriate for biomedical applications involving hyperthermia.

Development of Lead Free Magnetoelectric Materials for Magnetic Field Sensor applications

(100-x) Na0.5Bi0.5TiO3 (NBT)-(x) NiFe2O4 (NFO)(x = 0, 20, 40, 60, 80 and 100) composites are synthesized using conventional solid state reaction method. Crystal structure studies are performed by using X-ray Diffraction technique (XRD) and the Rietveld analysis of XRD patterns confirms the co-existence of cubic (NFO) and rhombohedral (NBT) symmetry with Fd- 3m and R3c space groups, respectively. Micro-structural study reveals the formation of combination of composite phases and its inter-coupling grains. The average grain sizes and area percentage of each phase for the composites are calculated using Image J software. The Magnetisation versus Magnetic field (M-H) hysteresis loops show soft magnetic behavior of composites with variation in Saturation magnetization (MS) and Coercivity (HC). A maximum MS (34 emu/g) and low HC (15 Oe) is obtained for (80) NFO - (20) NBT composite.The Polarization – Electric field (P-E) analysis shows that the maximum saturation polarization (PS) is obtained for (60)NBT-(40)NFO sample and is attributed to the leakage current generated by conductive NFO phase. The coupling between the ferrite and ferroelectric phase is studied based on the magnetoelectric voltage coefficient(αME). The maximum (αME) of 1.82 mV/cm-Oe is obtained for (80)NBT -(20)NFO sample and this is almost 80% higher than the previously published literature on NBT-NFO composites. This can be attributed to the uniform distribution of grains with each ferroelectric phase surrounded by ferrite phase as shown in the morphological study.

Sm-doped enhanced magnetic-dielectric properties of low-temperature fired Co2Z ferrite materials for high-frequency device applications

Co2Z ferrite with superior performance is a beneficial material for high filter devices and antenna substrates. In this work, Ba3Co2Fe24-xSmxO41 (x = 0.00–0.50 with a step of 0.10) materials were prepared using low temperature-fired process with 2.5 wt% of Bi2O3. The phase formation, microstructure, magnetic property, complex permittivity, and complex permeability were studied using X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, and vector network analyzer. The materials remained in a single hexagonal phase, and the grain size increased with increase of Sm-doped content. Saturation magnetization of samples increased at first and then decreased. When x = 0.20 and 0.30, the value of 4πMS was 2910.4 G and 2861.7 G, respectively. The variation of saturation magnetization is mainly due to the occupancy of Sm3+ ions. When Sm3+ ion doped Fe3+ ion of Co2Z ferrite, Sm3+ ion first preferred to occupy 4eIV site due to its low electronegativity, and then occupied 12k and 4f sites at high doped content, affecting magnetic moment and magneto-crystalline anisotropy. Furthermore, low-temperature sintering improves magnetic-dielectric properties of Sm-doped materials in high-frequency range. The real part of magnetic permeability (μ′) reached a maximum value of 8.4 when x = 0.20 and the real part of dielectric permittivity (ε′) reached a maximum value of 14.1 when x = 0.30. The magnetic loss and dielectric loss remained low (tanδμ = 0.05–0.08 and tanδε = 0.005–0.04) and the off-cut frequency was nearly 1 GHz. The results indicated that these magnetic-dielectric materials have great potential for high-frequency antenna applications.

Positron annihilation and magnetic studies of gamma irradiated nickel ferrite nanoparticles sintered at various temperature

The effects of gamma irradiation on structure and magnetic properties of nickel ferrite nanoparticles, prepared by the sol-gel method and sintered at 300, 500 and 900 °C, are studied through X-ray diffraction, positron annihilation lifetime spectroscopy, coincidence Doppler broadening spectroscopy and vibrating sample magnetometer. The prepared samples were irradiated with gamma rays from 60Co, 137Cs and 22Na for 1, 2 and 3 weeks that received 0.47, 0.94 and 1.41 rad dose of radiation. The XRD patterns showed that the prepared and irradiated samples are single phase with cubic spinel structure. The cation distribution, lattice constant, average crystallite size and lattice strain were obtained by the Rietveld refinement of XRD patterns and their variations with irradiation depend on sintering temperature and therefore the particle size. Scanning electron microscopy confirmed formation of nanoparticles. Positron annihilation lifetime and coincidence Doppler broadening measurements showed that for prepared samples with an increase in sintering temperature the size of vacancies increase while their concentrations decrease. It is observed that the effect of gamma radiation on samples depend on sintering temperature or particles size of samples. Also, the type of defects in sample sintered at 300 °C recognized different from samples sintered at 500 and 900 °C. Saturation magnetization and coercivity increased for prepared samples with increase in sintering temperature. The variations of saturation magnetization and coercivity with gamma irradiation for samples sintered at various temperature were different and explained with variation in cation distribution and surrounding environment of vacancies in samples. The measurements showed that samples with more vacancy concentration undergo more cation redistribution due to gamma radiation.

Structure, magnetism and large anomalous Hall effect of hexagonal MnYSn (Y = Ti, Mn and Fe) ribbons

Mn-based alloys have attracted considerable research interest in exploring new materials for the next generation of high-density and low-cost spintronic devices due to their variety of physical properties. The Ni2In-type Mn-based hexagonal alloys have been discovered for their potential application in martensitic phase transformation functional materials. However, the magnetotransport properties in these alloys have not been well studied. In this work, a comprehensive study including structure, magnetism and magnetotransport has been carried out on the Ni2In-type MnYSn (Y = Ti, Mn and Fe) alloys. The variation of saturation magnetization and Curie temperature in MnYSn alloys are analyzed. The anomalous Hall conductivity of MnTiSn and MnFeSn are dominated by the skew scattering mechanism, reaching 60 and 93 Ω−1 cm−1 at 5 K. The magnetotransport properties in MnYSn alloys suggest that it could be a potential candidate for magnetic sensors.

Magnetoelectric coupling lights up spintronics path: Lithium battery ideas to tune magnetism

Magnetoelectric coupling lights up spintronics path: Lithium battery ideas to tune magnetism

Intermixing induced anisotropy variations in CoB-based chiral multilayer films

We examine the atomic intermixing phenomenon in three distinct amorphous CoB-based multilayer thin film platforms — Pt/CoB/Ir, Ir/CoB/Pt and Pt/CoB/MgO — which are shown to stabilise room-temperature chiral magnetic textures. Intermixing occurs predominantly between adjacent metallic layers. Notably, it is stack-order dependent, and particularly extensive when Ir sits atop CoB. Intermixing induced variations in magnetic properties are ascribed to the formation of magnetic dead layer arising from CoIr alloying in the metallic stacks. It also produces systematic variations in saturation magnetization, by as much as 30%, across stacks. Crucially, the resulting crossover CoB thickness for the transition from perpendicular to in-plane magnetic anisotropy differs by more than 2 across the stacks. Finally, with thermal annealing treatment over moderate temperatures of 150–300 °C, the magnetic anisotropy increases monotonically across all stacks, coupled with discernibly larger H c for the metallic stacks. These are attributed to thermally induced CoPt alloying and MgO crystallization in the metallic and oxide stacks, respectively. Remarkably, the CoB in the Pt/CoB/MgO stacks retains its amorphous nature after annealing. Our results set the stage for harnessing the collective attributes of amorphous CoB-based material platforms and associated annealing processes for modulating magnetic interactions, enabling the tuning of chiral magnetic texture properties in ambient conditions.

Effect of heat treatment on structural and magnetic properties of Li–Ni ferrite prepared via sol–gel auto-combustion method

Nanocrystalline Li0.35Ni0.3Fe2.35O4 ferrites were prepared at different annealing temperatures by sol–gel auto-combustion method. The effects of the annealing temperature on the structure and magnetic properties of the synthesized Li–Ni ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared spectra and Vibrating Sample Magnetometer, and X-ray photoelectron spectrometer. Rietveld refinement of the XRD data confirmed the occurrence of phase transition from α-spinel to β-spinel, from which the ideal cation occupation and lattice parameter can be obtained. The grain size increased significantly with annealing temperature. The variation of saturation magnetization can be well explained in terms of the occupation of ions in tetrahedron and octahedron. The coercivity initially increased and later decreased significantly from 115 to 37 Oe with the increase of annealed temperature which could be attributed the fact that the 600 °C-annealed grain size is close to transition size from single- to multi-domain region.

Impact of ambient temperature on the switching of voltage-controlled perpendicular magnetic tunnel junction

Voltage control of the magnetic anisotropy (VCMA) effect enables a voltage-mediated magnetization switching mechanism for lower-power applications. In this work, we experimentally investigate the characteristics of VCMA-induced switching and we observe a clear decrease in the critical switching voltage (Vc) at elevated temperatures. A 50% reduction in Vc is quantified when increasing the ambient temperature (T) from 300 K to 360 K. Such a T-dependence of Vc is well explained with the variations of saturation magnetization (MS), interfacial anisotropy (Ki), and VCMA coefficient (ξ). In addition, the dependences of these properties on temperature are well fitted and explained with the power law of MS(T). Our findings on the T-dependent magnetic and switching characteristics of VCMA are of technological importance for implementing VCMA in magnetic random access memory (MRAM) applications.

A Study of Magnetic Properties of Manganite Substituted ZnFe2O4 Composites

Composites of ZnFe2O4/La0.67Sr0.33MnO3 with different weight percentages were synthesized using sol-gel method and their magnetic behavior was investigated. Powder X-ray diffraction studies show spinel structure for zinc ferrite and rhombohedral for La0.67Sr0.33MnO3. An additional minor phase of α −Fe2O3 and ZnO was also noticed in zinc ferrite suggesting non-stoichiometric nature. Fourier transform infrared spectroscopy studies display cohabitation of two phases belonging to ferrite and perovskite phase with varying peak intensities. Field-dependent magnetization measurement at room temperature shows partial variation in saturation magnetization and remanent magnetization values with increase in La0.67Sr0.33MnO3 weight percent in zinc ferrite. Except for zinc ferrite, $\left (\frac {dM}{dH}\right )$ shows single peak with smooth variation, pointing to easy rotation of magnetic dipoles under applied fields.

Study of magnetic and magnetoresistance behaviour of [formula omitted] composites

Nanocomposites of Lanthanum Strontium Manganite and Cobalt Ferrite with different weight percentages were prepared using the sol–gel method and sintered at 950 °C. Presence of constituent phases of La0.67Sr0.33MnO3 and CoFe2O4 peaks were confirmed from X-ray diffraction and Fourier transform infrared spectroscopy studies. Hysteresis behaviour shows room ferromagnetism for the composite samples and their variation in saturation magnetization can be understood on the basis of competing effects between both the magnetic phases. Enhancement of squareness ratio and coercivity indicate the strengthening of exchange-coupling interaction due to closer proximity of hard and soft phases. Metallic state vanishes and resistivity increases with the incorporation of cobalt ferrite into lanthanum strontium matrix. An enhanced magnetoresistance in a wide temperature range is observed for 25% cobalt ferrite added sample and is ascribed to spin-polarized tunneling mechanism. Adiabatic small polaron hopping mechanism is used to explain the resistivity of the composites in the high temperature region.

Realization of resistive and magnetization switching in sol-gel derived yttrium iron garnet thin films

In this work, large-area ferrite thin films of ferromagnetic yttrium iron garnet (Y3Fe5O12, YIG) were synthesized on Pt/Ti/SiO2/Si (Pt) substrates by a sol-gel method to investigate the resistive and magnetization switching properties. The synthesized YIG thin films acquire a single garnet structure. The Pt/YIG/Pt stack illustrates unipolar resistive switching behavior with excellent switching uniformity, large memory window (102), stable cycle-to-cycle endurance, and good data storage retention (104 s). The ~46% saturation magnetization variation could be realized via the conversion between high and low resistance states by manipulating the electric field. Schottky emission is governed in the high-field region for the high resistance state. Temperature dependence of resistance and magnetization variation confirms that oxygen vacancies conductive filament model and valence state change (Fe2+ and Fe3+) are responsible for the resistive and magnetization switching mechanisms. These results indicate that YIG ferrite based stack is suitable to design the electro-magnetic coupling multifunctional nonvolatile memory devices.

Investigation on structural, hysteresis, Mössbauer properties and electrical parameters of lightly Erbium substituted X-type Ba2Co2ErxFe28-xO46 hexaferrites

A series of Erbium substituted X-type Ba2Co2ErxFe28-xO46 (x = 0.00, 0.04, 0.08, 0.12, 0.16, and 0.20) hexaferrites were prepared by the method of heat treatment. The obtained precursors were heated at 1350 °C for 6 h. XRD investigation reveals that x = 0.0 sample possesses X, W-type, and α-Fe2O3 phases, while Er- substituted samples show presence of X and W phases. The room temperature Mössabuer spectra have been fitted with five sextets. A variation in saturation magnetization (MS) is explained and supported by the Mössbauer spectroscopy. The maximum values of MS (52.29 Am2/kg) and anisotropy field-Ha (1370 kA/m) are found for x = 0.12 composition. Similarly, the maximum relative area (~69%) for spin up sites (k+a+b) is also found for x = 0.12 composition. Low frequency (20 Hz–2 MHz) dielectric response of all samples show normal behavior of ferromagnetic materials. The dielectric measurements reveal that the conduction in low frequency is due to grain boundary contributions and at the higher frequency it is due to grain contributions. AC conductivity is found to increase with frequency in all prepared hexaferrites. The substituted compositions can have potential applications in filter application due to soft ferrite behavior and low dielectric loss tangent.

Gamma-irradiation induced modifications in structural and magnetic properties of nanocrystalline Mn0.5Zn0.5 SmxFe2-xO4 ceramics

The changes in structure, infrared absorption and magnetic property of nanocrystalline Mn0.5Zn0.5SmxFe2-xO4 (x = 0.01, 0.03 and 0.05) ceramics were studied after different doses (0, 15 and 25 kGy) of γ-irradiation. The samples were prepared by solution combustion route. We observed that up to the highest studied dose (25 kGy) of γ-irradiation all the samples retain the cubic spinel (Fd-3m) structure as of the pristine samples, however, the lattice parameter decreases. Furthermore, we observed the metastability of Sm (and Mn) atoms at the octahedral sites. By Sm3+ doping the saturation magnetization of the pristine samples decreases, but the magnetic coercivity increases drastically, indicating enhancement of magnetic anisotropy. After γ-irradiation the magnetic anisotropy vanishes completely and the sample behaves super-paramagnetically with a small variation in saturation magnetization. Our results are important to understand the behavior and stability of the magnetic hardness created by Sm3+ doping in soft magnetic Mn–Zn ferrite ceramics.

Magnetic behaviors of spinel ferrite nanoparticles: a Monte Carlo simulation

Iron oxide nanoparticles with different phases (α-Fe2O3, γ-Fe2O3 and Fe3O4) are classified as the substantial transition metal oxides taking advantage of technological importance. The results of a Monte Carlo study of magnetic ordering in selectively spinel nanoparticles are discussed. The classical spin model with the Heisenberg-type interactions was used with superexchange interaction term. Different types of selective structures were studied in the framework of crystalline spinel structures with perfect or disordered surface and dilution of octahedral sublattice. The results are compared for various degrees of magnetic competition between first neighbor’s interactions in inverse or mixed spinel nanoparticles. The results permit us to explain the variation in saturation magnetization and give a better insight into the complex interplay between cationic distribution and magnetic disorder in ferrimagnetic nanoparticles.

Effect of Mn addition on the structural and magnetic properties of Zn-ferrite nanoparticles

Abstract Super-paramagnetic, mono-dispersed and single-phased Mn-substituted Zn-ferrite nanoparticles (NPs) with a narrow size distribution were synthesized by a one-step citric acid-assisted hydrothermal method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and Fourier-transform infrared spectroscopy (FTIR) techniques were utilized to determine characteristics of the NPs. The as-prepared Zn0.3Fe2.7O4 NPs were highly crystalline with uniform size (14.5 ± 2.65) and good stability in an aqueous medium. The effects of Mn concentration (x = 0.25, 0.5, 0.75 and 1) and pH on the formation of Zn0.3MnxFe2.7−xO4 NPs were thoroughly studied. The maximum saturation magnetization of 55 emu/g was obtained for the Zn-ferrite sample substituted with x = 0.5 of Mn. Increasing x firstly resulted in an increased saturation magnetization from 47.1 emu/g (x = 0.25) to 55 emu/g (x = 0.5), followed by a decrease to 37 emu/g (x = 1). The variation of saturation magnetization was correlated with the distribution of Mn2+ ions in tetrahedral and octahedral sites.

Synthesis and Characterization of Nickel-Substituted Cobalt Ferrite Nanoparticles Using Sol–Gel Auto-combustion Method

In the present work, Co1−xNixFe2O4 (x = 0.02, 0.04, and 0.06 M) is prepared by sol–gel auto-combustion method and its structural, functional, magnetic, and morphological characteristics are analyzed. The peaks corresponding to the plane observed from XRD matches with JCPDS data of CoFe2O4 (22-1086) and NiFe2O4 (10-0325). It is noted that the average crystallite size decreases from 31 to 27 nm when the nickel concentration increases from 0.02 to 0.06 M, indicative of the incorporation of Ni2+ ion in the cobalt ferrite lattice. FTIR analysis shows the presence of M $\leftrightarrow $ O vibration at the tetrahedral and octahedral sites. Micro - Raman spectroscopy shows the stretching vibrations at 486.87 cm− 1 (Eg) and 696.96 cm− 1 (A1g), which are the characteristic vibrations of spinel ferrites. Magnetic studies show the variation in saturation magnetization (MS = 20.25, 9.41, 18.5 emu/g.) and coercivity (HC = 746.06, 953.03, 885.59 Oe) when the concentration of Ni2+ ion increases from 0.02 to 0.06 M. The prepared nanoparticles show a ferromagnetic nature which is attributed to the creation of an antiparallel spin and the magnetic moment created by the cation at tetrahedral and octahedral sites. The surface morphology of samples is imaged by a field emission scanning electron microscope.

Investigations of surface spin canting in Ni-Zn nanoferrite and its development as magnetic core for microwave applications

• Achieved high saturation magnetization of 80.3 emu/gm for a crystallite size of 42 nm. • Low surface spin canting angle observed is the cause for such high magnetization. • Initial permeability dispersion shows that the material would be suitable as magnetic core up to 18 GHz. Nanoparticles of nickel zinc ferrite Ni 0.65 Zn 0.35 Fe 2 O 4 having an average crystallite size of 42 nm, synthesized by sol–gel method were found to exhibit the highest value of saturation magnetization along with high dc resistivity. The observed variations in saturation magnetization and crystallite size as a function of annealing temperature were elucidated considering the core surface magnetic interactions and the particle shape of the nanoferrite using low temperature in-field Mössbauer measurements and the high-resolution transmission electron micrographs. With the attainment of valuable magnetization and resistivity, the usefulness of the material as magnetic core for high frequency applications has been investigated by studying the frequency dependence of initial permeability. Interestingly, the results support that the material would be suitable as magnetic core up to 18 GHz.