Room Temperature Magnetic Measurements Research Articles

Evolution of magnetization of Bi1-ySmyFe1-xTixO3 ceramics at the morphotropic phase boundary attested by multistep magnetization measurements, time aging and electric field

Bi1-ySmyFe1-xTixO3 ceramics with compositions at the rhombohedral- orthorhombic morphotropic phase boundary (y = 0.1, 0.12, 0 ≤ x ≤ 0.1) were prepared by solid state reaction method. Analysis of the crystal structure of the compounds based on the results of laboratory and synchrotron X-ray diffraction measurements as well as Raman spectroscopy experiments revealed a coexistence of the rhombohedral phase (SG R3c) and the anti-polar orthorhombic phase (SG Pbam) in the compounds Bi0.88Sm0.12Fe1-xTixO3 with 0 ≤ x ≤ 0.1; the compounds Bi0.9Sm0.10Fe1-xTixO3 are characterized by the mixed structural state for the concentration range 0 ≤ x ≤ 0.06 and by the single phase rhombohedral state within 0.06 < x ≤ 0.1. Room temperature magnetization measurements demonstrate a gradual increase of remanent magnetization with Ti content in the compounds of both systems up to the maximal value of MR ∼0.28 emu/g for compounds with x = 0.06 which is followed by a decrease in magnetization with further titanium doping. Temperature decrease leads to a reduction of remanent magnetization which is mainly caused by a partial recovery of spatially modulated spin structure occurred in the compounds of both systems. Time aging of the compounds for about ∼1 year leads to a drastic increase of MR, which is caused by a change in the structural phase ratio, homogeneity of the structural state and a contribution of unbounded spins demonstrated by low field measurements. Subjecting of the annealed compounds to external electric field of E ∼40 kV/cm leads to a decrease of magnetization associated with backward structural transformations and redistribution of the local structural defects in the compounds.

Synthesis, physico-chemical properties, and AC induction heating of polycaprolactone-coated bio-compatible Fe3O4 nanoparticles

Ex-situ functionalization of Fe3O4 nanoparticles, synthesized using a coprecipitation method, with bio-compatible polycaprolactone (PCL) polymer is reported in this study. The formation of the crystalline structure of Fe3O4 is confirmed from the X-ray diffraction patterns. The presence of the PCL polymer on the surface of the coated MNPs is confirmed using Fourier transform infrared and X-ray photoelectron spectroscopy techniques and thermogravimetric analysis. Scanning and transmission electron microscopy imaging studies reveal the nearly spherical morphology of the synthesized nanoparticles. Room temperature magnetization measurements show the superparamagnetic nature of the PCL coated nanoparticles with high saturation magnetizations varying from ∼61–66 emu/g. Further, the room temperature coercivity is found to be reduced by ∼78 % for the PCL coated nanoparticles, which is attributed to the lowering of the interparticle interactions upon surface functionalization. Magnetic fluid hyperthermia studies on the PCL coated nanoparticles dispersed in ∼1 wt% agar gel shows significant alternating magnetic field induced heating efficiency, with temperature rise in the vicinity of the hyperthermia limit (∼42 °C). The highest specific absorption rate is found to be ∼85.4 ± 3.9 W/gFe, indicating an intrinsic loss power of ∼0.62 nHm2kg−1, which is significantly higher than the previously reported values for PCL coated Fe3O4 MNPs. The field induced heating efficiency is found to be correlated with the saturation magnetization of the PCL coated nanoparticles. In vitro cytotoxicity studies on human breast cancer (MCF-7) cell lines confirm the superior bio-compatibility of the PCL coated Fe3O4 nanoparticles. Superior field induced heating efficiency, coupled with good bio-compatibility makes the PCL functionalized Fe3O4 nanoparticles a potential candidate for magnetic fluid hyperthermia.

Synthesis, Characterization, Fluorescence and Antibacterial Activities Studies of Transition Metals Complexes with a Macro Acyclic Schiff Base Ligand

The reactions of the Schiff base 2,2’-[(2-hydroxypropane-1,3-diyl) bis-(imino-methane diyl)] bis-(4-bromophenol) (H3L), with metal transition ions (Mn(II), Ni(II), Cu(II), Zn(II), and Cd(II),) afforded one type of complex formulated as [M(HL)(H2O)2].nH2O. These compounds have been characterized by elemental analysis, UV–Vis, FTIR, 1H and 13C NMR spectroscopies, molar conductivity and room temperature magnetic measurements. The structure of nickel (II) complex has been determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group Pnma with a = 7.7702(4) Å, b = 23.1921(15) Å, c = 10.6853(5) Å, V = 1925.57(15) Å3, Z = 8, R1 = 0.043 and wR2 = 0.107, Dcalc = 1.893 Mg m−3. The ligand acts in tetradentate fashion in its di-deprotonated form. Two coordinated water molecules complete the coordination sphere. The environment around the Ni(II) center is best described as an octahedral geometry. In the crystal structure of the Schiff base ligand, the existence of a strong intramolecular O-H•••O hydrogen bonding [O2W-H2W 0.80(3) Å, H2W •••O1 1.915(3) Å, O2W••• O1 2.6258(19) Å, O2W-H2W•••O1 148(3)°] and [O1W-H1W 0.73(3), H1W•••O1 2.15(4) Å, O1W•••O1 2.836(2)Å, O1W-H1W•••O1 156(4)°] are observed. Antibacterial activity study shows that the cadmium (II) complex is more active than the free ligand on.

Porous Silicon and Silicon Nanotubes with Embedded FePt Nanoparticles Investigated by High Temperature Magnetic Measurements

Porous silicon (PSi) and silicon nanotubes (SiNTs) are presented as a platform for filling with FePt nanostructures. The difference of the magnetic characteristics between the two systems is figured out. Furthermore, the FePt filled templates are compared with the same template materials filled with Ni/Co by electrodeposition.The porous silicon is produced by anodization of a highly doped n-type silicon wafer in a 10 wt% HF solution. The produced morphology offers separated pores of about 50 nm and a mean distance between the pores of 50 nm. The SiNTs are fabricated in using an array of ZO wires as template, subsequent silicon deposition and finally etching off the ZO. The inner diameter of the tubes and also the wall thickness can be tuned by the fabrication process. In this work SiNTs with comparable inner diameter to the PSi structure and a wall of about 10 nm are used (1). FePt nanoparticles (NPs) are deposited electroless inside the pores and the tubes, respectively whereat the molar ratio of Fe is varied. For this purpose a 3 component solution consisting of H2PtCl6, Fe(NO3)3 and citric acid is used, whereas the ratio of the components is modified.The varying magnetic response of the different composite systems, porous silicon and silicon nanotubes is investigated. PSi/FePt shows a higher coercivity and remanence than SiNTs/FePt and thus a higher hard magnetic performance. The variation of the coercivities between SiNTs/FePt and PSi/FePt is about 57%.Considering the FePt deposits with different molar ratio of Fe the coercivities vary in a range of 5% in the case of both template types. Comparing FePt loaded samples with Co loaded samples in all cases an increase of the coercivity and of the remanence is observed for FePt, whereat in the case of PSi as template material the increase is significantly stronger than in the case of SiNTs samples. Figure 1 shows the comparison of the hysteresis of PSi and SiNTs filled with FePt NPs.The influence of high temperatures on the nanocomposite samples is of interest, as well as the high temperature magnetic behavior. Therefore, beside low temperature and room temperature magnetic measurements, the magnetic behavior of the samples is investigated at high temperatures up to 1273 K.(1) K. Rumpf, et.al, ECS Transactions 98 (2020) 37

Synthesis and Characterization of Co(II), Ni(II), Cu(II) and Zn(II) Complexes with N'-( phenyl ( pyridin-2-yl)methylene)Nicotinohydrazide

The Schiff base (HL), derived from 2-benzoylpyridine and nicotinic hydrazide, and its complexes with some metal transition (Co, Ni, Cu, Zn) have been synthesized. These compounds have been characterized by means of elemental analysis, 1H and 13C NMR (for HL), FTIR spectroscopy, UV–Vis spectroscopy, molar conductance and room temperature magnetic measurements. The compounds are found isostructural and are formulated as {[Co(L)2].2H2O} (1), {[Ni(L)2].2H2O} (2). {[Cu(L)2].3H2O} (3). {[Zn(L)2].H2O} (4). The two ligand molecules act in their monodeprotonated forms through one azomethine nitrogen atom, one pyridine nitrogen atom and one iminolate oxygen atom yielding six coordinate metal center. The complex 4 crystallizes in the monoclinic space group P21 with cell parameters of a = 9.3429(8) A, b = 10.3034(9) A, c = 16.6349(14) A, β = 101.109(4)°, V = 1571.3(2) A3, Z = 2, R1 = 0.027, wR2 = 0.074. The zinc atom is six-coordinated, and the coordination polyhedron is best described as a distorted octahedral geometry. The aromatic rings of the ligand molecules are twisted each other with dihedral angle values in the range 10.168(2)°–74.430(1)°.

Fabrication and Characterization of Ni-Carbon nanofibers by Electrospinning Technique

Carbon nanofibers with the distribution of magnetic Ni metal (Ni-CNFs) have been synthesized using Nickel (II) acetate tetrahydrate (Ni (OCHCH3)2.4H2O), polyacrylonitrile (PAN) as precursors by electrospinning technique. The as-prepared nanofibers were dried in a vacuum oven, stabilized, and followed by carbonization at 850 °C in N2 atmosphere. Their structural phase composition, microstructure, and magnetic properties have been investigated. The phase formation of pure Ni-CNF without any impurity has been confirmed by X-ray diffraction (XRD) pattern. The average diameter of the nanofibers and the Ni nanoparticles has been calculated to be 159±25.72 nm and 67±11.24 nm, respectively. Energy-dispersive X-ray spectroscopy (EDX) measurement has been carried out to confirm the presence of Ni and C elements with their weight%. Raman spectrum attributes the presence of two characteristic absorption peaks of carbon materials. Room temperature (300 K) magnetic measurement shows the ferromagnetic behavior of Ni-CNF. These nanofibers have the potential to be used in a wide variety of applications including These materials have wide variety of applications as in different magnetic devices (magnetic sensors, magnetic recording devices, and soft magnetic materials.), microwave absorption materials, supercapacitors and batteries etc.

Magnetic properties of gadolinium and/or dysprosium substituted Sm–Co nanocomposite ribbons

The present study reported the influence of heavy rare-earth elements (Gd and/or Dy) on Sm-Co-based melt-spun ribbons. Microstructure and magnetic properties of Sm-Co-based (Sm1–xRExCo5) ternary and quaternary systems were investigated. The X-ray diffraction, Auger spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses reveal the presence of the 1:5H and 2:17R phases in the as-spun ribbons. A high-temperature magnetic measurement reports a Curie temperature (TC) at ∼825 and ∼869 K in Sm0.6Gd0.4Co5 (ribbon A) and Sm0.6Gd0.3Dy0.1Co5 (ribbon B), respectively. A low-temperature magnetic measurement on Sm0.6Gd0.3Dy0.1Co5 ribbons exhibits a type-2 SR (spin reorientation) behaviour at ∼72 K, which arises due to the presence of the DyCo5 phase. Room temperature magnetic measurements reveal that overall magnetic measurement (OMP) is about 24 and 29.9 for ribbons A and B, respectively. Consequently, the comparative investigations profess that ribbon B shows better magnetic performance due to Dy addition with reduced grain size. This observation indicates that the Gd and Dy substituted Sm–Co magnet can be a potential magnet for high-temperature applications.

Impacts of annealing temperature on microstructure, optical and electromagnetic properties of zinc ferrites nanoparticles synthesized by polymer assisted sol-gel method

Nanocrystalline zinc ferrite (NZF) were successfully synthesized at different calcination temperature via sol-gel method from the precursor salt solutions using tartaric acid and PVA solution as a chelating agent and binder respectively. The characterization of NZF and their properties had been investigated using sophisticated techniques viz. X-ray diffraction, Fourier transform infra-red spectroscopy, Scanning electron microscopy, Transmission electron microscopy, Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV–Vis-NIR spectroscopy, Vibrating sample magnetometer and Impedance analyzer. X-ray peak profile analysis through Debye Scherer and Wilson method, Halder-Wagner method has been used to estimate the structural parameters. The crystallite size and particle size of ZnFe2O4 samples were found to increases with increasing annealing temperature while lattice parameters and lattice strain decreases. Dynamic light scattering and zeta potential measurements were used to evaluate the particle size distribution and stability of these systems. The room temperature magnetic properties measurement showed that the net magnetic moment is observed for NZF due to cation distribution although the bulk ZnFe2O4 is non-magnetic. Direct optical band gaps of the prepared NZF samples has been investigated by UV–Vis NIR spectroscopy using Tauc formula and found that energy band gaps (Eg) values are in a narrow range of 1.19–1.86 eV. The frequency dependent dielectric properties, impedance and modulus spectroscopy measurement has been investigated in the frequency range of 100 Hz to 20 MHz. The synthesized NZF particles will be applied for Gas sensor, humidity sensor and photocatalyst.

Unraveling the effect of Gd doping on the structure, optical, magnetic, dielectric and photocatalytic properties of ZrO2 nanostructures

Nanocrystalline Zr1-xGdxO2 (0≤x ≤ 0.20) samples were synthesized through the sol-gel combustion process and characterized by various characterization techniques.XRDanalysis confirms a highly crystalline tetragonal phase with P42/nmc space group. TEM micrographs exhibitreduction in particle size on Gd doping. Photoluminescence (PL) study shows improved light absorption ability of the Gd-doped ZrO2, signifying an excellent way to control the recombination rate of electron-hole pair. XPS analysis ensures the successful incorporation of Gd in the ZrO2 lattice. Room temperature magnetic measurements revealthe ferromagnetic nature of all the samples. The UV-visible spectroscopy shows increase in band gap from 3.82 eV to 4.45 eV. The dielectric constant varies significantly for the Gd-doped samples. All the prepared catalysts were tested for the photocatalytic activity of the methylene blue (MB) dye under visible light irradiation. After 120 minutes, 20% Gd-doped ZrO2displays∼91% degradation efficiency against the MB dye, which makes it a promising visible light-activated photocatalyst.

Ce substituted NiCo[formula omitted] microspheres and nanoflakes: Comparison on magnetic features

NiCo2−xCexO4 (0.0 ≤ x ≤ 0.08) microspheres (MCs) and nanoflakes (NFs) were synthesized hydrothermally. X-ray diffraction analysis confirmed the cubic microstructure of all the samples. The microsphere and nanoflake morphologies of the samples have been confirmed by SEM, along with EDX, TEM and HR-TEM. The magnetic properties of the NiCo2−xCexO4 (0.0 ≤ x ≤ 0.08) MCs and NFs were investigated via magnetization measurements using a vibrating sample magnetometer. Room-temperature magnetization measurements revealed weak ferromagnetic behavior for both MC and NF samples. Low temperature magnetization measurements showed strong ferromagnetic behavior for the different samples. The magnetic parameters for both samples were found to differ substantially at a given temperature, which is accredited to the differences in the morphology of the MC-like and NF-like samples. Room-temperature magnetization measurements revealed antiferromagnetic or paramagnetic behavior for MC samples and weak ferromagnetic character for NF samples. It was also found that the magnetization magnitude decreased with increasing cerium dopant level, when compared to the host product. The changes in magnetization are linked to the effect of introduced cerium ions and their magnetic states, which could generate structural/morphological changes, changes in the size and surface lattice, redistribution of cations among the crystal lattices, changes in magnetic moment, etc.

Influence of Fe3+ by La3+ cations substitution on the crystallography and magnetic properties of yttrium iron garnet compound

In the present study, we have investigated the influence of La3+ cations insertion on the crystallography, morphology, and magnetic properties of Y3Fe5-xLaxO12 compound, (x = 0.00 and 0.03) obtained by the sol-gel method. To confirm the Fe3+ by La3+ cations replacement and quantify the structural parameters, the Rietveld refinement method was used. The quantitative analysis confirmed that, the La3+ cations insertion in the YIG crystal structure affect significative the lattice constant, crystallite size, microstrain, sites occupancy, bond angles and distances. Room temperature Raman spectra also confirmed the YIG single phase structure. The spectra deconvolution pointed shifts for smaller wavenumber in the sample containing La3+ cations, specifically in the region between 400 and 800 cm−1, correlated with the octahedral and tetrahedral sites. The coral format morphology was confirmed by Scanning and Transmission Electron Microscopies. Lastly, room temperature magnetic measurements demonstrated that the La3+ cations insertion in the YIG crystal structure, provokes an increase in the saturation magnetization (Ms), remanent magnetization (Mr) and magnetocrystalline anisotropy (K1) of 24.8, 17.5, and 9.3%, respectively, respect to the values obtained for undoped YIG sample.

Preparation, Characterization of Some Lanthanide(III) Complexes of N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide

The present investigation describes the synthesis and structural study of the ligand N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HL), which was used to generate two type complexes formulated as [Ln(HL)2(NO3)2(H2O)].(NO3) (Ln = La (1) and Pr (2)) and [Ln(HL)2(NO3)(H2O)2].(NO3)2 (Ln = Nd (3), Sm (4), Gd (5) and Tb (6)). The ligand and the complexes are characterized by NMR, UV-Visible and FTIR spectroscopies, conductivity measurements and room temperature magnetic moment measurements. The [La(HL)2(NO3)2(H2O)].(NO3) compound crystallizes in the orthorhombic space group Pbcn with the following unit cell parameters: a = 16.8634(8) Å, b = 8.0615(4) Å, c = 30.2833(15) Å, V = 4116.8(3) Å3, Z = 8, R1 = 0.049 and wR2 = 0.120. The structure reveals that two neutral ligand molecules in η3-mode, two bidentate nitrate groups in η2-mode and one water molecule coordinate the central La3+. Each organic molecules acts through one carbonyl oxygen atom, one azomethine nitrogen atom and one nitrogen atom from a pyridine ring. The lanthanide ion has a coordination number of 11 and the coordination environment can be described as distorted pentacapped trigonal prism. Numerous hydrogen bonds link the molecules into three-dimensional network.

Optical and temperature-dependent magnetic properties of Mn-doped CoFe2O4 nanostructures

Understanding and untangling magnetic materials are essential to implanting these materials for practical industrial applications. This work demonstrates how manganese (Mn) doping can significantly advance cobalt ferrite's magnetic and optical characteristics. We applied the hydrothermal approach to synthesize cobalt ferrite nanostructures, followed by Mn doping, to acquire CoMnxFe2−xO4 (0 ≤ x ≤ 0.1) nanostructures. The crystal structure of all the specimens confirms the formation of Fd-3 m space growth with a typical cubic structure. The estimated crystallite size values vary between 19.8 and 25.8 nm, and the lattice parameter significantly enhances from 8.31 Å to 8.38 Å as a result of Mn substitution. The fast Fourier transform infrared spectroscopy (FTIR) was performed between 400 and 4000 cm-1. The lattice vibrations ranging υ1 = 614–607 cm-1 and υ2 = 428–426 cm-1 were assigned to tetrahedral and octahedral sites, respectively. The high-resolution transmission electron microscopy (HRTEM) analysis further confirms the crystalline structure of CoMnxFe2−xO4. The room temperature magnetic measurements investigate that the magnetic coercivity of CoMn0.2Fe1.8O4 nanostructures is maximum (∼ 800 Oe) which was opted for temperature-dependent measurements. The low-temperature magnetic characteristics agree with Bloch's and Kneller's laws for saturation magnetization and coercivity of CoMn0.2Fe1.8O4 nanostructures. The optical properties confirm a blueshift and slight increment in bandgap energy of CoMnxFe2−xO4 nanostructures.

New Fe(III) Trichlorido Complex of a Bidentate N'-(thiophen-2-ylmethylene)isonicotinohydrazide Ligand: Synthesis, X-ray Structure, Spectral Characterization, and Electrochemistry Study

Fe(III) complex of the hydrazone from (E)-N'-(thiophen-2-ylmethylene)isonicotinohydrazide (HL) has been synthesized and characterized by elemental analysis, electrical conductance in non-aqueous solvents, FT-IR and electronic spectroscopies, room temperature magnetic measurement, electrochemistry study as well as by X-ray diffraction structure determination. In the complex, the ligand acts in its neutral bidentate form, coordinating through the carbonyl oxygen and azomethine nitrogen. A high spin octahedral geometry assigned to the Fe(III) complex were further confirmed by room temperature magnetic moment data. Elemental analysis showed that Fe(III) complex is composed of metal and ligands in a molar ratio of 1:1. This complex of Fe(III) is a neutral electrolyte in DMF solution. The electrochemistry study shows that a one electron process determined the electrochemical reaction is governed by an electron transfer with an irreversible process. The structure of the complex has also been determined by X-ray diffraction revealing an octahedral environment around the Fe(III) ion.

Spectroscopic Studies and X-ray Structural of Dinuclear Lanthanide (III) Complexes Derived from N&amp;apos;-(2-hydroxy-3-methoxybenzylidene) Nicotinohydrazide

Two Schiff bases (H₂L), derived from o-vanillin and nicotinic hydrazide, and its complexes with some lanthanides (Y, Ce, Yb, Pr, Gd and Tb) have been synthesized. These compounds have been characterized by means of elemental analysis, UV–Vis spectroscopy, FTIR spectroscopy, ¹H and ¹³C NMR (for H₂L), molar conductance and room temperature magnetic measurements. The compounds are found isostructural and are formulated as {[(Z)(<i>η</i>²-OOCH₃)Ln](<i></i>-L)₂[Ln(<i>η</i>²-OOCH₃)(Z)]} (Z = H₂O for Ln = Y, Ce, Pr, Gd or Tb and Z = OS(CH₃)₂for Ln =Yb). The two ligand molecules act in their dideprotonated forms through one azomethine nitrogen atom, one phenoxo oxygen atom and one iminolate oxygen atom. The two Ln (III) ions are bridged by two phenoxo oxygen atoms, forming a dinuclear complex. Single crystal X-ray analysis of the ytterbium complex has revealed the nature of the structure {[(OS(CH₃)₂)(<i>η</i>²-OOCH₃)Yb](<i></i>-L)₂[Yb(<i>η</i>²-OOCH₃)(OS(CH₃)₂)]} (3). The complex crystallizes in the monoclinic space group C2/c with cell parameters of <i>a</i> = 13.0391(6) Å, <i>b</i> = 15.1199(6) Å, <i>c</i> = 20.7239(7) Å, <i>β</i> = 105.671(2)°, <I>V</I> = 3933.8(3) ų, <I>Z</I> = 4, <I>R</I>₁ = 0.025, <i>wR</i>₂ = 0.65. The ytterbium atoms are eight-coordinated, and their coordination polyhedron are best described as a square antiprismatic geometry. The aromatic rings of the ligand molecule are twisted with dihedral angle of 29.23 (1)° between their mean planes.

Influence of Dysprosium Doping on Structural, Magnetic, and Optical Properties of Ni–Zn Ferrites

The spinel ferrites with the compositional formula Ni0.8Zn0.2Fe2−xDyxO4 (x = 0, 0.004, 0.008, 0.012, 0.016) have been prepared using the sol–gel method. The X‐ray diffraction measurements confirm the cubic spinel structure of the sample with a space group of Fd‐3m. Morphological analysis of scanning electron microscope images reveals that the particles are spherical in shape. Energy dispersive X‐ray spectroscopy (EDX) confirms the elemental composition. Thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) analysis of synthesized dysprosium (Dy) doped Ni–Zn ferrites are carried out from 25 to 700 °C. Fourier‐transform infrared (FTIR) spectroscopy studies reveal the stretching and bending vibrations of the various bonds presented in the compounds. The UV–vis absorption spectrum indicates the energy gap values which small decrease with the Dy concentration increase. Raman spectroscopy reveals the crystal distortion and phases of the samples. The room temperature magnetic measurements (M–H loops) are carried out to study the effect of Dy doping on magnetic properties.

Investigation on structural, magnetic and optical properties of Sm–Co Co-substituted BiFeO3 samples

Abstract Sol–gel derived Sm–Co co-substituted BiFeO3 ceramics (Bi1–x SmFe1–x Co x O3 with x = 0.0, 0.01, 0.02 and 0.03; named as BFO, BSFCO-1, BSFCO-2 and BSFCO-3, respectively) were investigated for structural, vibrational, magnetic and optical properties. Distorted perovskite rhombohedral structure with R3c crystal symmetry has been established in X-ray diffraction (XRD) patterns analysis by Rietveld refinement and detailed structural parameters like lattice constants, unit cell volume, bond angles, bond length etc. have been evaluated. Raman spectra further confirmed typical rhombohedral structure of BiFeO3 by exhibiting 13 clear Raman active phonon (9E + 4A) modes along with second order modes in the wave number range 50–1500 cm−1. Fourier Transform Infrared (FTIR) spectra showed the presence of Fe–O and Bi–O bands and the calculated Fe–O bond length was in good agreement with that obtained from Rietveld analysis. Room temperature magnetization versus magnetic field (M–H) measurement using Vibrating Sample Magnetometer (VSM) showed enhancement of ferromagnetic ordering parameters with increasing Sm–Co content in BiFeO3 samples. The maximum magnetization values increased from 0.237 emu g−1 for BFO sample to 1.167 emu g−1 for BSFCO-3 sample along with increase in remnant magnetization values. The optical property of Bi1–x SmFe1–x Co x O3 samples was investigated by estimating the energy band gap using UV–Visible spectroscopy. The calculated values of energy band gap were varied in the range 2.46 eV–1.81 eV indicating tuning of energy band gap with Sm–Co co-substitution in BiFeO3 sample.

Effect of Zn2+-Sn4+ co-substitution on structural and magnetic properties of SrFe12-2xZnxSnxO19 (x = 0–2) M-type strontium ferrite

We studied the structure and magnetic properties of Zn2+-Sn4+ co-substituted M-type strontium ferrite by X-ray diffraction (XRD), Fourier transformer infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and superconducting quantum interference device magnetometer (SQUID-VSM). The lattice constants a and c increase monotonically with increasing substitution x, which is primarily attributed to the fact that the ionic radii of Zn2+ and Sn4+ are larger than those of Fe3+. The room temperature magnetic measurement results indicate that the saturation magnetization (Ms) can reach the maximum value Ms = 77 emu/g when x = 0.25, originating from the occupation of Zn2+ and Sn4+ in the spin-down 4f1 and 4f2 sites, respectively. Next, when x ≥ 0.5, the nonmagnetic Zn2+ and Sn4+ weaken the superexchange interaction, resulting in a monotonic decrease in saturation magnetization and coercivity. The sample with x = 0.25 has the optimum magnetic properties of Ms = 77 emu/g, Mr = 35 emu/g and Hc = 2203 Oe, and it is a promising candidate for high-density magnetic recording materials.

Direct evidence for weak ferromagnetism sustained by Fe2+–O–Fe3+ superexchange coupling in short-range structures of aluminosilicate glasses

We report on the magnetism of amorphous SiO2–Al2O3–CaO–MgO–Fe2O3–K2O–MnO:CA (CA—activated carbon) aluminosilicate glasses prepared by a fusion-quenching method. Fourier transform infrared and Raman spectroscopy show that a Fe2+ lattice modifier in the glass structures induces depolymerization, strongly influencing the magnetic transitions. Room temperature magnetization measurements of the CA-glasses show a different magnetic behavior, such as speromagnetism, asperomagnetism, and weak ferromagnetism. Mössbauer spectroscopy analyses at room temperature reveal that iron changes valence from Fe3+ → Fe2+ with increasing CA content. This Fe3+ → Fe2+ suggests that asperomagnetism and weak ferromagnetism behavior are triggered by Fe2+–O–Fe3+ superexchange coupling in short-range structures of aluminosilicate glasses. A model for the aluminosilicate glass structures is proposed to explain the different magnetic regimes.

Influence of Na/Mg Co-Doping in Tuning Microstructure, Transport, Optical, and Magnetic Properties of TiO2 Compounds for Spintronics Applications

In recent years, researchers have been making a persistent effort to discover innovative and appropriate oxide materials that can be exploited in optoelectronics devices. The primary objective of this research is to study the effect of Na/Mg co-doping on microstructure, transport (dielectric and Hall Effect), optical and magnetic properties of Ti0.94-yNa0.06MgyO2 (y = 0–0.08) compounds that were synthesized using a solid-state route method. All the compounds have been crystallized to a single rutile phase, as reported by the XRD study. The elemental color mapping reveals that there is a consistent distribution of all of the elements across the compound. The XPS study suggests that Ti mostly resided in the Ti4+ oxidation state. The enhancement of the Mg co-doping concentration led to a decrease in the dielectric value as well as the AC conductivity of the material. In addition to this, it has been noted that these compounds have a low dielectric loss. The analyses of Nyquist plots reveal that the increase of Mg co-doping concentration led to a rise in the amount of relaxation that is non-Debye sort. This, in turn, caused a reduction in the amount of resistance exhibited by grains and grain boundaries. The Maxwell–Wagner model was used to conduct an analysis of the dielectric data, and the results indicated that the hopping of charge carriers is most likely to be responsible for the transport of electrical charges. From the optical properties’ measurement and analyses, it was noticed that the band gap had been slightly changed, but the transmittance value had increased from 81% for Ti0.94Na0.06O2 to 84% with an increase in Mg co-doping concentration. The Hall Effect analysis unequivocally pointed to the presence of p-type conductivity as well as an increased carrier density concentration. The room temperature magnetization versus field measurement indicates the ferromagnetic nature of the samples. Thus, the co-doping of Mg with Na in TiO2 leads to a narrowing of the band gap of TiO2 while tweaking the optical and transport properties. The studied materials can be utilized for spintronics and optoelectronics applications.