Magnetic Hysteresis Curves Research Articles

Determination of anisotropy constants via fitting of magnetic hysteresis to numerical calculation of Stoner–Wohlfarth model

Anisotropy constants of magnetic materials are typically determined through angle-resolved Ferromagnetic Resonance (ar-FMR) and torque magnetometry, which can be time consuming measurements, thus limiting their utility. The Stoner–Wohlfarth model can be used to numerically fit measured magnetic hysteresis curves to more easily determine these anisotropy constants. To demonstrate this, 10 nm bct FexCoyMnz single-crystal films grown by molecular beam epitaxy on MgO(001) substrates were investigated. The hysteresis behavior measured by vibrating sample magnetometry was least-squares fit against numerically calculated hysteresis curves generated from the Stoner–Wohlfarth model to extract the anisotropy constants. The cubic anisotropy of different compositions of FeCoMn films was at ∼104 J/m3, which is on the same order of magnitude of bct Fe and Co thin films measured by ar-FMR and torque magnetometry techniques.

Tunable multiferroic and forming-free bipolar resistive switching properties in multifunctional BiFeO3 film by doping engineering

The advent of multiferroic-based materials has opened the plethora for high tunable multifunctional materials and ultra-fast operation for future non-volatile memory technology. Multifunctional rhombohedral Bi0.94Y0.06Fe0.95Mn0.05O3 (BYFMO) film is grown on fluorine-doped tin oxide to investigate the electromechanical and resistive switching properties in Ag/BYFMO/FTO RRAM configuration. UV–visible absorbance spectra reveal the semiconducting behavior of BYFMO, and the band-gap is found to be 2.37 eV. The magnetic hysteresis curve manifests the soft ferromagnetic nature by suppressing the spiral spin modulated structure, supported by MFM imaging. The Y-Mn co-doped BFO possesses highly tunable piezoelectric and ferroelectric features with maximum domains preferred along 710 and 1090. Lateral domain growth is observed with the increase in tip bias voltage. The Ag/BYFMO/FTO RRAM shows distinct bipolar resistive switching behavior at the SET (ON), and RESET (OFF) processes are obtained at voltage VSET = +1.7V and VRESET = −2.8V, respectively. The memory window (ON/OFF) between high resistance state and low resistance state is about ~ 100, which can be sustained up to 100 testing cycles and 103s without any degradation, indicating that the BYFMO based device exhibits better endurance and retention properties. Moreover, the resistive switching mechanism of the device can be well explained by space charge limited current conduction, which is well supported by conducting a filamentary model. With excellent piezoelectric and resistive switching performance, the multifunctional BYFMO has enough potential for future non-volatile memory technology.

Perpendicularly magnetized ferromagnetism in Mn/Al bilayer thin films on Si substrates induced by temperature dependent ion beam mixing

The perpendicularly magnetized τ-phase was achieved in Mn/Al bilayer thin films by ion beam mixing using 400 keV Xe ions. The effect of annealing and irradiation on the structural, microstructural, and magnetic properties of Mn/Al bilayer thin films was investigated in the present study. Mn/Al bilayer thin films (thickness ∼97 nm) were deposited on silicon substrates by the evaporation technique. These as-deposited films were irradiated to the fluences of 5 × 1016 and 1 × 1017 ions cm−2 at three substrate temperatures (Room temperature ∼300 K, 450 K, and 623 K). As-deposited films were also annealed at 450 K and 623 K for 5 h. The ferromagnetic τ-phase was enhanced in annealed and irradiated thin films confirmed from synchrotron x-ray diffraction patterns, MFM images, and magnetic hysteresis curves. The average grain size estimated from the AFM study was found in the range of 78–192 nm. The domain patterns obtained in MFM images confirmed the ferromagnetic nature of the annealed and irradiated films. The hysteresis curves measured at 5 K show the maximum coercivity (7111 Oe) for the sample annealed at 450 K and the highest value of saturation magnetization (60 emu cc−1) for the film irradiated to the fluence of 1 × 1017 ions cm−2 at the substrate temperature of 450 K. Perpendicularly magnetized τ-phase was achieved in the films irradiated to the fluence of 1 × 1017 ions cm−2 at different temperatures. The formation of the ferromagnetic phase by ion beam mixing can be attributed to the combined effect of ballistic mixing and thermal spike mechanisms. This study suggests that the ferromagnetic properties of MnAl thin films can be modified by selecting the proper annealing and irradiation conditions to make them useful for applications in spintronics and magnetic memory devices.

Magnetic Reversal in Wiegand Wires Evaluated by First-Order Reversal Curves.

The magnetic structure of Wiegand wires cannot be evaluated using conventional magnetization hysteresis curves. We analyzed the magnetization reversal of a Wiegand wire by measuring the first-order reversal curves (FORCs). A FeCoV Wiegand wire with a magnetically soft outer layer and a hard magnetic core was used in this study. The magnetization reversal of the soft and hard regions in the wire was identified in the FORC diagrams. The magnetization reversal of the dominantly irreversible process of the soft layer and the magnetic intermediate region between the soft and hard regions was clarified.

Mn and Al co-doped CdS:Cr nanoparticles for spintronic applications

Nowadays, diluted magnetic semiconductors with improved ferromagnetic feature is utterly seeking for use in modern spintronic applications.We describe the optical as well as magnetic properties of CdS, CdS:Cr, CdS:(Cr + Al), and CdS:(Cr + Mn) co-doped samples. The substitution of Cr dopant and co-dopant ions (Al and Mn) in the host sites were confirmed through structural analysis. Declining of energy band gap with the incorporation of Cr dopant and co-dopant ions (Al and Mn) into the CdS host lattice was estimated through optical studies. Room-temperature magnetic hysteresis curves revealed that pure CdS exhibited paramagnetic nature due to its surface defects, whereas CdS:Cr, CdS:(Cr + Al), and CdS:(Cr + Mn) co-doped nanoparticles showed better ferromagnetic characteristics. Among all synthesized nanoparticles, CdS:(Cr + Al) semiconductor sample exhibited enhanced ferromagnetic nature and may benficial for spintronic applications.

Dielectric and Magnetic Studies La+3 doped Cobalt Nano Ferrite

La3+ substituted cobalt ferrite nano-particles with the chemical composition LaxCoFe2-xO4 (here,x=0, 0.05, 0.1, 0.15 and 0.2) were synthesized using auto-combustion method. Structural and morphological studies were probed using X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). Formation of rare-earth doped cobalt ferrite was confirmed using the X-ray diffraction studies. Average crystallite size (D) was found to be varying from 43.71nm to 55.37nm with the increase in La3+ concentration. Frequency dependent dielectric properties of synthesized samples were measured from 100 Hz to 1 MHz at room temperature using a precision HIOKI make LCR HI-TESTER. Dielectric dispersion was observed at lower frequencies for the synthesized samples. Magnetic properties were studies using Vibrating Sample Magnetometer (VSM), all the synthesized samples exhibited well defined magnetic hysteresis curves, there by confirming the magnetic behaviour of the sintered samples.

Fabrication and Characterization of α-Fe2O3 Nanoparticles Dispersed Epoxy Nanocomposites

Hematite(α-Fe2O3) nanoparticles were synthesized by sol-gel process and further mixed with epoxy resin to obtain the nanocomposites. X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analysis revealed that α-Fe2O3 nanoparticles have an average diameter of about 30 nm, also illustrated the crystal structure and morphology of the nanomaterials. Fourier-Transform Infrared spectroscopy (FTIR) showed the functional groups that were present in α-Fe2O3 nanoparticles, neat epoxy andα-Fe2O3/epoxy nanocomposites. Vibrating Sample Magnetometer (VSM) analysis exhibits the magnetic hysteresis curve and revealed that α-Fe2O3 nanoparticles were superparamagnetic. Tensile testing was performed to obtain the tensile strength, yield strength, elongation, young modulus and required energy to deform the materials. Vickers micro-hardness test showed the surface hardness of the nanocomposites. Flexural strength also measured, which indicate the strength of nanocomposites against bending. Thermogravimetric Analysis (TGA) measurement showed the thermal properties of α-Fe2O3 nanoparticles and its influence into the epoxy matrix. UV-Vis spectroscopy was performed to obtain the optical band gap energy of the nanocomposites. DC-resistivity measurements showed a significant influence of α-Fe2O3 nanoparticles on the dc-electrical properties of the epoxy matrix.

Electric, magnetic and microstructural features of the La2CoFeO6 lanthanide ferrocobaltite obtained by the modified Pechini route

In the search for new materials with applicable magnetic properties in spintronic devices, the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La2CoFeO6 using the modified Pechini route; the experimental study of structural, morphological and magnetic properties, and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional Theory. Rietveld refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure, space group [Formula: see text]21/[Formula: see text] (# 14). Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline, with mean grain sizes between 177 and 188 nm. The dispersive X-ray spectroscopy suggests that the material obtained contains La, Fe, Co and O in the stoichiometric proportions expected by up to 98%. The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically, showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO6 and CoO6 octahedra. Magnetic hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated, up to room temperature. I–V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor type. The ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.

Influence of ball milling parameters on microstructure and magnetic properties of aluminum bronze chips reinforced with vanadium carbide

This article analyzes the influence of mechanical ball milling parameters on processed aluminum bronze chips in order to increase the efficiency of this process in terms of particles' size reduction. Also evaluated is the addition of vanadium carbide (VC) in this response, along with its microstructure and magnetic properties. The experiments have been carried out in accordance with DOE design methodology. After machined, its residues can still be reused to produce composites through powder metallurgy routes, preserving good mechanical properties without onus to the environment. The study aims to produce and characterize powders resulting from ball milling processes, identifying the influential parameters, in addition to verify its soft magnetization behavior. The powder morphologies and particle sizes underwent scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS) and laser diffraction particle analyses, respectively, in addition to phase identification via X-ray diffraction (XRD). Moreover, saturation magnetization (Ms), remanent magnetization (Mr), coercivity (Hc), and remanence-to-saturation ratio (Mr/Ms) were determined through magnetic hysteresis curves obtained from a vibrating sample magnetometer (VSM). Results indicate that % VC and milling time are the main parameters to improve the milling efficiency and obtain submicrometric particles with sizes almost 800 times smaller than the initial chips. After the milling process, aluminum bronze powders presented certain amorphization, a decrease of about 24% in Ms and an elevation about 81% in Hc, both compared with the as cast material. The Mr/Ms ratio indicates a slight conservation of magnetization.

Synthesis and characterization of nanoparticles Zn0.7Ni0.15Cu0.15Fe2O4 using the co-precipitation method

This research was conducted to see the nanostructure and magnetic properties of nanoparticle Zn0.7Ni0.15Cu0.15Fe2O4. Zn0.7Ni0.15Cu0.15Fe2O4 has been successfully synthesized at 100°C using co-precipitation method. After synthesized, it was dried at 80°C. The second step, nanoparticle powder was characterised by X-Ray Diffraction (XRD) to determine the structure and phases formation of Zn0.7Ni0.15Cu0.15Fe2O4. FE-SEM was used to analyze the morphology of Zn0.7Ni0.15Cu0.15Fe2O4. To find out the elements contained in the sample, EDAX testing was conducted. X-Ray Diffraction (XRD) results showed that Zn0.7Ni0.15Cu0.15Fe2O4 in the shape of cubic spinel with the main peak at (311). There was a hematite phase (Fe2O3) with low intensity. Zn0.7Ni0.15Cu0.15Fe2O4 crystallizes well indicated by 2θ = 35.385°. The crystal size on the nano scale has been formed, which was 14.5087 nm. The FE-SEM results showed that the morphology of Zn0.7Ni0.15Cu0.15Fe2O4 was spherical and has agglomerated. The elements contained in these nanoparticles were Zn, Ni, Cu, Fe and O. There were no other impurities indicated from the EDAX test results.This indicated that the elements contained were already in accordance with the chemical formula. Magnetic hysteresis curves showed that Zn0.7Ni0.15Cu0.15Fe2O4 was softmagnetic.

Investigation on interatomic chemical bonding and charge-related optical, multiferroic properties of La1−xZnxFeO3 bulk ceramics

A series of Zn-substituted La1−xZnxFeO3 (x = 0.00, 0.05, 0.15, and 0.25) bulk ceramics was prepared using solid-state reaction method. The XRD patterns and profile refinements confirm the orthorhombic phase formation in La1−xZnxFeO3. The charge density distribution in the La1−xZnxFeO3 unit cells were analyzed qualitatively and quantitatively. The average particle size and energy band gap were determined using the SEM images and UV–Visible absorption spectra. The magnetic hysteresis (M − H) curves show weak ferromagnetic order and shift in the hysteresis curves. The Zn-substituted system (x = 0.25), exhibits relatively high dielectric constant with low dielectric loss. Ferroelectric measurements show the rectangular-like P-E loops with Barkhausen jumps. In this work, the effect of Zn-substitution on the crystal lattice and hence the modified optical, and multiferroic properties of LaFeO3 have been examined through charge density analysis which has not been investigated so far.

A facile method to produce magnetic nanoparticles and its influence on their magnetic and physical properties

This work presents a rapid and facile method to produce and adjust the magnetic and physical properties of magnetic nanoparticles. SEM and DRX characterizations, as well as magnetic hysteresis curves and magnetic susceptibility curves, were performed to study changes in the nanoparticles as a function of two stirring speeds: 1000 and 3000 rpm. The formation of spherical nanoparticles was observed at both speeds, but the small ones (72 nm) were obtained at the highest stirring speed. However, at this speed, the magnetite nanoparticles showed to be partially oxidized to hematite. Magnetic curves reveal the superparamagnetic and spin-glass behavior of both kinds of nanoparticles. The blocking and irreversibility temperature of the nanoparticles was not perceived even at room temperature.

Evaluation of Cu–MgFe2O4 spinel nanoparticles for photocatalytic and antimicrobial activates

Organic pollutant discharges to water bodies are found to be toxic. A simple chemical co-precipitation method has been adopted for the preparation of Cu–MgFe2O4 nanoparticles, because photocatalysts can extract dye pollutants from wastewater. Phase evaluation, microstructure, magnetic and electrical properties were studied. The spinel structure was examined by the X-ray diffractometer (XRD) and the approximate crystalline sizes ranged from 12 to 44 nm. The morphology of the prepared products was documented by the transmission electron microscope (TEM). Magnetic hysteresis (M-H) curves were performed using a vibrating magnetometer sample. The coercive value (Hc) increases while the saturation magnetization (Ms) decreases with the substitution of Cu2+. Room temperature DC electrical and AC conductivity tests were carried out for all materials. The antibacterial activity of Cu–MgFe2O4 NPs was studied using Agar well diffusion method and the samples MCFO-2 and MCFO-3 NPs showed maximum antibacterial activity compared to MCFO-1 NPs (minimum activity) against Micrococcus luteus (Gram positive) and Escherichia coli (Gram negative). Photo-Fenton operation was performed using organic methylene blue (MB) to analyze the dye removal efficiency of spinel Cu–MgFe2O4 nanoparticles.

Crystalline, ferromagnetic-semiconductor and electronic features of the terbium-based cobalt-ferrite Tb2FeCoO6

Ceramic samples of Tb2FeCoO6 were synthesized by the solid-state reaction recipe. The crystallographic analysis revealed that the material crystallizes into a complex perovskite-type orthorhombic structure (space group P21/n, # 14) with octahedral distortions. The surface topography of the material was evaluated by means of scanning electron microscopy, observing densified submicrometric granular characteristics in the form of polyform sheets. Energy scattering spectra showed 98% agreement between the experimental composition and the stoichiometry of the Tb2FeCoO6 formula. The DC magnetization curves as a function of temperature exhibit irreversible behavior at low temperatures related to the distortionary character of the Fe–O6 and Co–O6 octahedra in the structure. Magnetization hysteresis curves as a function of the applied field at temperatures from 5 K up to 300 K reveal a ferromagnetic type ordering in the material. The I–V characteristic suggests a semiconductor electrical response with a varistor-type tendency and strong dependence of the polycrystalline nature of the samples. Calculations of band structure and density of electronic states predict the semiconductor characteristic for this double perovskite, with Eg = 2.48 eV and the ferromagnetic behavior is attributed to extended super-exchange spin interaction in the Fe–O–Co ions. The ferromagnetic semiconductor nature of the Tb2FeCoO6 material foresees potential applications in the novel spintronics industry.

Characterization and synthesis of Fe3O4@C nanoparticles by in-situ solid-phase method

Fe3O4@C nanoparticles were successfully synthesized by an in situ solid-phase method using FeSO4, FeS2, and PVP K30 as the starting materials under the nitrogen atmosphere. In addition, the mechanism of the synthetic of Fe3O4@C nanoparticles was studied through in situ characterizations. The results showed that the pyrolysis of PVP K30 participated in the solid-phase reaction and resulted in the formation of carbon shells and a reduction in particle size. The structure of the Fe3O4@C nanoparticles was core–shell with the average particle size of ∼30 nm and the thickness of the carbon shell of ∼2 nm. Besides, the Raman spectrum revealed that the carbon shell mostly existed in the form of amorphous carbon. The surface area and the pore volume of the Fe3O4@C nanoparticles were estimated to be 37.74 m2 g−1 and 0.227 cm3 g−1. Magnetization hysteresis curve exhibited the values of coercivity and remanence and saturation magnetization are found to be approximately 0.16 kOe, 12.8 emu g−1, and 77 emu g−1, respectively.

Simbang Darah (Iresine herbstii) extract mediated hydrothermal method in the synthesis of zinc ferrite spinel nanoparticles used for photocatalysis and antibacterial applications

This paper reports the use of Simbang Darah (Iresine herbstii) leaf extract to synthesize ZnFe2O4 spinel ferrite nanoparticles via hydrothermal method. Biochemical compounds in Simbang Darah leaf extract act as a capping agent and a stabilizer to form nanostructures. XRD patterns and FTIR spectrums confirm the formation of the cubic spinel crystal structure of ZnFe2O4 nanoparticles. SEM and TEM characterization revealed that ZnFe2O4 spinel ferrite morphology has a uniform spherical shape in nanoscale. EDX results showed that the compositional mass ratios were relevant as expected from the synthesis. ZnFe2O4 nanoparticles have an absorption edge in the visible region with Eg values within the range 2.05–2.11 eV in the DRS UV–Vis analysis. The as-prepared samples exhibit paramagnetic behavior according to the magnetic hysteresis curve. ZnFe2O4 nanoparticles were proven effective in direct red 81 dye photodegradation (99.66%) after exposure to solar light irradiation for two hours. On top of that, ZnFe2O4 nanoparticle exhibited antibacterial activity against S. aureus and E. coli.

Detail investigation of thermoelectric performance and magnetic properties of Cs-doped Bi2Sr2Co2Oy ceramic materials

Bi2Sr2−xCsxCo2Oy materials with 0 ≤ x ≤ 0.15, have been fabricated via the classical ceramic technique. XRD results have indicated that undoped and Cs-substituted samples are composed of Bi2Sr2Co2Oy phase as the major one. Microstructural studies have demonstrated the formation of a liquid phase, which allows a drastic grain growth. This factor is responsible for a drastic improvement of relative density, reaching about 95% of the theoretical one for 0.125 Cs content. On the other hand, electrical resistivity has been reduced up to 14 mΩ cm at 650 °C for 0.125 Cs content, around 40% lower than the obtained in undoped samples. As a consequence, Seebeck coefficient has been decreased due to the raise in charge carrier concentration. The highest power factor at 650 °C (0.21 mW/K2 m) has been found for 0.125 Cs substituted sample, about 40% larger than the obtained in undoped samples, and very similar to the notified in single crystals (0.26 mW/K2 m). Magnetisation with respect to temperature results have demonstrated that measured samples have a paramagnetic property above 50 K, except 0.10 Cs. Magnetic hysteresis curves have shown that the slopes and the magnitudes have increased with decreasing temperature.

Analysis of magnesium ferrite and nickel doped magnesium ferrite thin films grown by Spray Pyrolysis

The magnetic magnesium ferrite (MgFe2O4) with a partially inverse spinel structure has been prepared by the classic ceramic method, which have practical application in information storage systems, magnetocaloric refrigeration and magnetic diagnostics. Nickel-magnesium ferrites (Ni:MgxFe3-xO4 or Mg(1-x)NixFe2O4; 0 ≤ x < 1) are magnetic materials of technological significance due to low electrical conductivity, low magnetic coercivity and low eddy current deceives. Magnesium plays an important role in the electrical and magnetic properties of Mg(1-x)NixFe2O4. Thin films were synthesized on different substrates with Spray Pyrolysis (SP) technique. The thin films were analyzed through Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and UV–Vis double beam spectrophotometer and for magnetic properties of films were used Vibrating-sample magnetometer (VSM) technique. In this study, the film is doped with material having magnetic properties and non-magnetic material. The change in the magnetic properties of the film will be examined as a result of the doping. As a result, the magnetic hysteresis curve of the film was changed by doping. Investigation of magnetic properties is very important for magnetic device applications such as magnetic recording, in magnetic sensor technology and room temperature giant magnetoresistance (GMR) applications.

The functionalization of Mn0.25Fe2.75O4/Ag-CMC/PVA ferrogel as antibacterial agent

Abstract Series of ferrogel samples have been successfully fabricated by using the freezing-thawing role. The filler used in ferrogel was magnetic material of Mn0.25Fe2.75O4/Ag synthesized by the co-precipitation method and chemical reduction. Whereas, the matrix used in ferrogel was a polymer composite of Carboxymethyl Cellulose (CMC) and Polyvinyl Alcohol (PVA). The characterization of the Mn0.25Fe2.75O4/Ag powder was carried out by using X-ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM), and antibacterial activities. The Mn0.25Fe2.75O4/Ag-CMC/PVA ferrogel was successfully characterized by antibacterial activity using the agar diffusion method. The XRD pattern of the Mn0.25Fe2.75O4/Ag powder illustrates the peaks owned by Fe3O4 and silver phases. Meanwhile, the magnetization hysteresis curve of the Mn0.25Fe2.75O4/Ag shows a decrease from 20.74 to 15.53 emu/g along with the addition of Ag material. Through the agar diffusion method, the Mn0.25Fe2.75O4/Ag powder and Mn0.25Fe2.75O4/Ag-CMC/PVA ferrogel samples showed excellent antibacterial activity as indicated by the widening of zones that were not overgrown with bacteria around the samples. Thus, the Mn0.25Fe2.75O4/Ag powder and Mn0.25Fe2.75O4/Ag-CMC/PVA ferrogel are potential for use in the biomedical field.

Improvement in photovoltaic response of bismuth ferrite by tuning its ferroelectric and bandgap properties

Pristine and Mn-doped bismuth ferrite samples were prepared by sol–gel method. XRD patterns showed rhombohedral to orthorhombic phase transition with Mn doping in BiFeO3 sample. The surface morphology of the samples was carried out by scanning electron microscope which exhibited a decrease in grain size with Mn doping. Magnetic hysteresis curves exhibit that manganese doping induces modification in magnetic properties of bismuth ferrites. Significant modification was observed in dielectric with Mn doping and maximum value was recorded for BiFe0.8Mn0.20O3 sample. P–E hysteresis curves were recorded to evaluate the ferroelectric properties of all samples at room temperature. A significant improvement was observed in ferroelectric properties in doped samples. Bandgap values of BiFe1−xMnxO3 in UV–Vis region decreases with Mn doping and minimum for BiFe0.80Mn0.20O3 sample as evaluated from Tauc’s plots. I–V studies of pristine and Mn-doped samples were carried out with light and without light. Enhanced photocurrent density was observed in Mn-doped BFO samples. Hence, these modifications in ferroelectric and photovoltaic properties of BiFe1−xMnxO3 samples make bismuth ferrites a good candidate for photovoltaic applications.