Law Of Approach To Saturation Research Articles

Unveiling the magnetic and optical properties of barium bismuthate thin films with distinct Ba/Bi ratios

This research aims to investigate the optical and magnetic properties of BaBiO3 (80:20), BaBiO3 (50:50), and BaBiO3 (30:70) thin films obtained by the polymeric precursor method. For better sample designations, the following codes were employed: (80:20) (BBO82), (50:50) (BBO55), and (30:70) (BBO37). The observed properties for barium bismuthates thin films were elucidated in terms of bismuth and oxygen vacancies as well as grain morphology, which can be controlled by stoichiometric changes (Ba/Bi ratios). According to the x-ray results the films crystallize in a rhombohedral BaBiO3 structure with an R-3R space group without any secondary phase as confirmed by Rietveld analyses. According to the photoluminescence results, x-ray photoelectron spectroscopy measurements as well as the law of approach to saturation (LAS), there are a significant presence of oxygen vacancies and vacancy clusters [BiO5.Vo.] in the films with high proportion of bismuth. The optical and magnetic properties developed by these films are originated from the following factors: tilting of BiO6 clusters which changes the length and angle of Bi–O–Bi bonds, creating a magnetic field responsible for the distinct Mr/Ms ratios, the formation of bipolarons caused by charge transfer between [BiO6] and [BiO5. Vo⋅] due to the oxygen vacancies formation, plate-like morphology which makes the domains easier to be switched under an applied external field resulting in a superparamagnetic behavior, charge disproportionation of various valence states (Bi+3 and Bi+5). Based on these results, new potential devices can emerge as possible tools to be applied in switches, actuators, spintronics, magnetic field sensors, etc.

Structural, thermodynamic, and magnetic properties of SrFe12O19 hexaferrite modified by co-substitution of Cu and Gd.

A hard magnetic system of SrFe12O19 nanomaterial was modified according to the composition of Sr0.95Gd0.05Fe12-xCuxO19 with x = 0.0, 0.30, and 0.60 using the sol-gel technique. The structures of the samples were evaluated using X-ray diffraction (XRD) along with Rietveld refinement, and an M-type hexaferrite with a hexagonal structure was confirmed with a trace amount of the α-Fe2O3 phase. In addition, transmission electron microscopy (TEM) analysis revealed polycrystalline nanoplates in all samples. Furthermore, the bond structures of the octahedral and tetrahedral sites along with the thermodynamic properties of these ferrites were extracted from the FTIR spectra at room temperature. The Debye temperature (θD) decreased from 755.9 K to 749.3 K due to the co-substitution of Gd3+ at Sr2+ and Cu2+ at Fe3+. The magnetic hysteresis (M-H) measurements revealed that the coercivity decreased from 5.3 kOe to 1.5 kOe along with the highest magnetization saturation (Ms) of 65.2 emu g-1 for the composition Sr0.95Gd0.05Fe11.7Cu0.3O19, which is suitable for industrial application. The effect of local crystalline anisotropy in magnetization was explored using the law of approach to saturation (LAS). Finally, thermo-magnetization was recorded in the range from 400 K to 5 K for cooling under zero field and in the presence of a 100 Oe field, and magnetic transitions were tracked due to the introduction of the foreign atoms of Gd and Cu into SrFe12O19.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.

Structural, magnetic, dielectric, magneto-electric and ferroelectric properties of BaTiO3- NiFe2O4 multiferroics

Multiferroics having composition yNiFe2O4 - (1-y) BaTiO3(y = 0.10, 0.30 and 0.50) have been prepared through the solid-state reaction route. These samples constitute NiFe2O4 as the ferromagnetic phase and BaTiO3as the ferroelectric phase. The X-ray diffraction (XRD) has been carried out to investigate the crystal structure formation and phase purity of the prepared ceramic samples. Rietveld refinement of XRD patterns confirm the presence of cubic (Fd3m) and tetragonal (P4mm) symmetries in all the samples. The effect of ferrite (NFO) concentration on magnetic, dielectric, ME coefficient and ferroelectric properties of samples has been studied further. The recorded M-H loops at room temperature, reflects the ferromagnetic nature of all samples. These hysteresis loops are fitted by LAS (law of approach to saturation), and the values of various magnetic parameters are evaluated. A gradual enhancement in magnetic parameters is noticed with an increased in NFO concentration. Variations of dielectric constant (ɛ') and loss tangent (tan δ) as a function of frequency as well as of temperature at various selected frequencies (10 kHz, 100 kHz, 500 kHz, and 1 MHz) have been studied. The highest value of magnetoelectric (ME) response has been observed for thesample0.10NiFe2O4-0.90BaTiO3. P-E loops show an enhancement in both the coercive field and the remnant polarization with an increment in ferrite content at room temperature.

Nanocrystalline Mn-doped Ni–Cu ferrites with a high cut-off frequency and initial permeability: Suitable for advanced electronic devices and biomedical applications

The microstructural and electromagnetic properties of Mn-doped Ni0.50-xMnxCu0.50Fe2O4 (x = 0.0, 0.10, 0.20, 0.30, 0.40) magnetic nanoparticles are studied. Compositions are produced by the combustion method, and samples prepared from these powders are sintered at different sintering temperatures. The Rietveld refinement of X-ray diffraction (XRD) data confirmed that all compositions have cubic spinel structures with an Fd-3m space group. The average crystallite size is within 8–65 nm measured by different methods. The porosity of the surface, average grain diameter, and grain distribution are measured using optical micrographs. The high cut-off frequency of 10 MHz is observed in the initial permeability as a function of frequency plots. The maximum Curie temperature of 855 K is found for the x = 0 sample. The maximum relative quality factor (2636) and lowest relative loss factor (0.04) are found for x = 0.4. The initial permeability as a function of frequency is also measured at liquid nitrogen temperature (77 K). The “law of approach to saturation (LAS)” is used for magnetization data and the highest saturation magnetization value 61 emu/g is obtained for x = 0.3. The "Jonscher universal power law" fitted the ac electrical conductivity with large dispersion at a higher frequency region and a small polaron hopping model is applicable in this case. The dielectric constant exhibit dispersive behavior at low frequency and follow Koop's as well as Maxwell-Wagner's two-layer models. At 100 Hz the maximum value of the dielectric constant is 2.8 × 105. Nyquist plot representation stated that the electrical conduction mechanism in these ferrites is mainly due to the influence of the grain and grain boundary effects. An electrical equivalent circuit is suggested to explain the impedance analysis. Electric modulus studies confirm the non-Debye type relaxation process of the compositions. Tuning all of the properties specifies that the synthesized magnetic nanoparticles may be an optimistic application for high-frequency electronic devices and biomedical applications.

Probing into the physicochemical consequences of pristine and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles for bactericidal, antifungal and hemolytic competency

Nano-scaled transition metal oxides are massively gaining an exciting horizon of research interest among material scientists by triggering scientific attention due to its prime advancements in physico-chemical, magneto-optical, electro-chemical, bio-medical and bio-compatible characteristics. The current work highlights the fabrication and formalisation of pure and X0.06Ni0.94O (X = Co, Fe, Cu) nanoparticles via bottom-up sol-gel pathway employing citric acid as the gelling factor. The crystallite size evaluated from X-Ray Diffraction (XRD) analysis decreased with respect to doping were estimated by successive systems among which Halder-Wagner (H-W) and Wagner-Agua (W-A) approach delivered prime results. Fourier Transform Infra-Red (FTIR) spectroscopy analysis regulated at room temperature in the mid infrared frequency continuum 400–4000 cm−1 confirmed the cubic conformation and the presence of predicted functional groups in the as-synthesized nanoparticles. The bandgap energy calculated from Ultra Violet-visible (UV–vis) spectroscopy is found to decrease for Co-NiO and Cu-NiO nanoparticles and increased for Fe doped NiO nanoparticles in comparison with the bandgap of pure NPs reasoned out by the Burstein-Moss shift. The device dependent parameter Urbach energy, and other pivotal optical parameters crucial in the fabrication of optoelectronic devices were evaluated. Surface morphological features and porous network of doped nanoparticles were investigated from Scanning Electron Microscopy (SEM) technique. Energy Dispersive X-ray (EDX) spectra ascertained the molecular matrix array and elemental composition in synthesized samples. The surface area measured from Brunauer-Emmett-Teller (BET) analysis revealed higher surface area (42 m2/g) for Fe-doped NiO nanoparticles than other counterparts. The thermal decomposition and stability of the pure and doped samples were analysed by Thermo-Gravimetric (TG) studies. The fundamental kinetic and thermodynamic parameters such as entropy, enthalpy, activation and Gibb’s free energy were elucidated through six different models viz., Coats-Redfern (CR), Piloyan-Novikava (PN), Horowitz-Metzger (HM), Van-Krevelen (VK), MacCallum-Tanner (MT) and Broido methods. Vibrating Sample Magnetometer (VSM) analysis coupled with the Law of Approach to Saturation (LAS) operandi extracted two critical magnetic criteria and the saturation magnetization is noticed to reduce with doping. The antibacterial and antifungal efficacies of the as-synthesized NPs were deeply discussed by portraying the nanoparticles-microbes interface. Iron and copper doped nickel oxide nanoparticles encountered favorable antimicrobial activity against pathogenic organisms. Furthermore, the bio-compatibility nature of the NPs was examined through hemolytic activity and the samples exhibited non-toxic behavior towards human cells till 50 μg/ml.

Theoretical and experimental investigations: Synergetic effect of Yb–Cu substitution on different properties of hexagonal ferrites

This research project was designed to understand the synergetic effect of trivalent ion Yb3+ and divalent ion Cu2+ co-substitution on different properties of X-type hexagonal nano ferrites. For this purpose, a series of Sr2-xNi2YbXFe28-YCuYO46 X-type hexagonal nano ferrites with concentration (x = 0, 0.02, 0.06, 0.1 & y = 0, 0.1, 0.2, 0.3) was synthesized by adopting the sol gel method. The XRD (X-ray diffraction) results of synthesized samples reveal the formation of single phase for all samples with space group P63/mmc. All the XRD peaks coincided with the reference card (ICDD # 01-073-2034). The theoretical fitting was performed by implementing the Rietveld refinement method to further check the single phase of the samples. The crystallite size and unit cell volume decrease with increasing Yb3+ and Cu2+ contents. The VSM results indicated the hard magnetic nature of all the synthesized materials and theoretically calculated particle size was varied in the range between 9.2 and 11.5 nm. The saturation (Ms) and remanence magnetization (Mr) decreased with the increase in Yb–Cu contents. The value of coercivity (Hc) was first increased and then decreased with the substitutions. Furthermore, the Law of approach to saturation (LAS) was employed to theoretically fit the hysteresis loops. The mixture of spherical and rod shape grains was observed in the SEM micrographs. By adopting the line intercept method, the calculated grain size was varied in the range from 0.691 to 1.33 μm. FTIR spectrum exhibits no extra absorption band due to residual material which also confirms the formation of single hexagonal phase structure. The Thermogravimetric (TGA) analysis divulged the weight losses due to removal of nitrate, vaporization of water molecules and removal of organic compounds at different temperatures. The reflection loss (RL) values have been enhanced with the substitution of Yb–Cu contents.

Comprehensive Law‐of‐Approach‐to‐Saturation for the Determination of Magnetic Anisotropy in Soft Magnetic Materials

Magnetocrystalline anisotropy is a crucial parameter that determines the suitability of magnetic material in a wide range of emerging applications. The law‐of‐approach‐to‐saturation (LAS), utilized to obtain the magnetocrystalline anisotropy from hysteresis loops, is not satisfactory for materials with cubic anisotropy as they are two orders higher than the bulk value. Herein, a modified formulation to LAS is presented, where the reduction in effective magnetic anisotropy (K) values due to Fe oxide phases in Fe particles over wide size ranges is accounted. The value ofKdecreases from 4.2 × 104 J m−3for the Fe particles of average size 210 nm to 1.2 × 104 J m−3for the 20 nm particles due to the increase in the iron oxide fraction with size reduction. The effective magnetic anisotropy obtained from the modified LAS has been validated from the ferromagnetic resonance studies for particles of the smallest size.

Magneto-thermal properties of Co-doped maghemite (γ-Fe2O3) nanoparticles for magnetic hyperthermia applications

We report the preparation, characterization, and heating efficiencies of undoped and Cobalt (Co)-doped maghemite (γ-Fe2O3) nanoparticles (NPs) for magnetic hyperthermia applications. The structural, magnetic properties and heating ability of the as-synthesized NPs were fully characterized. XRD and Rietveld analysis showed the formation of single cubic phase of γ-Fe2O3, where doping with Co did not alter either the crystal structure or the lattice parameter. It was found that Fe ions are tetrahedrally and octahedrally coordinated to oxygens and that Co ions occupy the octahedral sites in Co-doped samples. Magnetic measurements displayed increase of magnetic saturation (Ms) with increasing Co concentrations from 0 to 5% (53.14–67.49 emu/g), with negligible coercive field and remanence suggesting superparamagnetic behavior. Langevin model and the law of approach to saturation (LAS) were used to confirm superparamagnetism and to determine the effective anisotropy constant (Keff), respectively. Temperature rise under an alternating magnetic field (AMF) were conducted, indicating that all the samples have high heating efficiencies and reach hyperthermia temperatures (42 °C) in relatively short times (3–10 min). Interestingly, γ-Fe2O3 NPs reached 42 °C in only ∼4 min, while 1–5% Co-doped γ-Fe2O3NPs required ∼ 7–10 min to reach the same temperature. Surprisingly, SAR (122 W/g) and ILP (1.5 nHm2/kg) values of γ-Fe2O3 NPs were found to be higher compared to Co-doped γ-Fe2O3 counterparts, indicating better heating efficiency of γ-Fe2O3 NPs. The mechanism of heating and plausible reasoning for this observation is discussed. Nevertheless, the ILP values for both γ-Fe2O3 and 1–5% Co-doped γ-Fe2O3 NPs (0.52–1.5 nHm2/kg) are in the range reported for commercial ferrofluids, proving their good heating efficiencies, and making them promising candidates for magnetic hyperthermia applications.

Uncovering the replacement of Zn2+ ions on nano-structural, opto/magneto/electrical, antibacterial and antifungal attributes of nickel oxide nanoparticles via sol-gel strategy

Transition metal oxides have gathered momentum among the scientific community on account of their peculiar procession in physico-chemical, opto-electronic, magnetic, electro-chemical, and biological attributes resulting from anisotropic charge distribution of partly filled d-orbitals, non-stoichiometric behaviour, and diverse oxidation states of the cations. The current work emphasize on the systematic synthesis and characterization of pristine and zinc (Zn) incorporated nickel oxide (NiO) nanoparticles in varying concentrations ZnxNi1-xO (x=0, 0.1, 0.2, and 0.3) via a scalable sol-gel approach assisting citric acid (C6H8O7) as a congealing factor. A series of extensive analyses were executed to investigate the structural, opto-electrical, and magnetic characteristics of prepared nanoparticles. X-Ray Diffraction (XRD) studies confirmed the face-centered cubic structure of as-synthesized samples and the corresponding crystallite size is found to decrease with an increasing dopant concentration as estimated from the Scherrer method. Scanning Electron Microscopy (SEM) studies portrayed the spherical structure and porous nature of NiO nanoparticles. Particle size calculated from SEM shows the decreasing trend with dopant discrepancy which is in accordance with crystallite size measured from XRD results. Energy Dispersive X-ray (EDX) spectra revealed the presence of estimated molecular assembly in synthesized samples. The cubic configuration and the presence of functional groups existing in synthesized nanoparticles were endorsed from Fourier Transform Infra-Red (FTIR) spectroscopy operated in the vibrational IR frequency region. The optical absorption spectrum examined from Ultra Violet-visible (UV–vis) spectroscopy evaluates the energy bandgap and it is noticed to increase from 2.48 to 2.87 ​eV affirming the Burstein Moss shift. The energy dispersion of optical parameters plays a crucial contribution in optical materials pursuant to its prominence in optical communications and in fabricating novel devices for spectral dispersion. Optical and energy dispersion parameters evaluated from Wemple-DiDomenico (WDD) model and non-linear optical parameters were deliberated from optical studies. The performance of integrated optical systems such as monochromatic filters, optical and electrical switches, laser diodes, detectors, and amplifiers can be controlled by the dispersion parameters. Urbach energy and another pivotal optical criterion highly correlated with the bandgap energy anchored in the fabrication of optoelectronic devices were assessed. The electrical characteristics such as dielectric constant, loss, and conductivity exhibited by pure and Zn doped nickel oxide nanoparticles were reported. Molecular electronic polarizability assessed through elementary solid-state parameters is in better concurrence with diverse relations like Clausius-Mossotti, Lorentz-Lorent, bulk modulus, optical electronegativity, and energy band gap. The pore size distribution of substance matrix and the associated surface area were elucidated from Brunauer-Emmett-Teller (BET) analysis. Dispersive magnetic properties and two pivotal parameters were derived from the Law of Approach to Saturation (LAS) operandi. Further, microbial cell mechanism was illustrated through nano-architecture design, and the antibacterial and antifungal activity encountered by undoped and zinc doped NiO nanoparticles against different microbial strains were deeply discussed for pilot production of antimicrobial agents.

Law of Approach to Saturation for Determining Magnetic Intrinsic Behavior of BaFe12-xMnx/2Tix/2O19 and SrFe12-xMnx/2Tix/2O19

The problem with permanent magnetic materials of very high anisotropic fields is that it is still difficult to determine the intrinsic magnetic properties, when measured using a magnetometer which has a limited magnetic field. The Law of Approach to Saturation (LAS) mathematical model provides a way to measure permanent magnets, with high anisotropic fields by correcting the magnetization data of the first quadrant curve or the virgin curve of the minor hysteresis loop. In this research, a computational LAS program was conducted to compute the intrinsic magnetic properties of magnetic materials, such as saturation magnetization, anisotropy field and magnetocrystalline anisotropy constant. Magnetization data were obtained from permagraph measurements of barium hexaferrite (BaFe12O19), strontium hexaferrite (SrFe12O19) and microwave absorbers BaFe12-xMnx/2Tix/2O19 and SrFe12-xMnx/2Tix/2O19. The convergences of magnetization were assessed to determine the effect of substitution on barium hexaferrite and strontium hexaferrite materials on saturation magnetization values, anisotropy constants and anisotropic fields.

Optimization of structure-property relationships in nickel ferrite nanoparticles annealed at different temperature

In this report, a detail analysis of the impact of annealing temperature on the structural, elastic, morphological, optical, and magnetic behavior of NiFe2O4 nanoparticles prepared by the citrate sol-gel method is presented. Analyzing the XRD patterns by the Rietveld method confirms that all the annealed samples have been crystallized to cubic spinel structure belonging to Fd3−m space group with a single phase. Rietveld analysis demonstrates the change in structural and microstructural parameters and movement of cations from tetrahedral to octahedral sites and vice-versa upon annealing. The quantitative estimation of Ni2+ & Ni3+ and Fe2+ & Fe3+ has been carried out using XPS analysis. Decreases in peak broadening and shift of five Raman active peaks towards higher frequency upon annealing have been analyzed using the phonon confinement model. The variation in elastic parameters with annealing temperature has been assessed by FTIR analysis. The UV analysis reveals the increase of the optical energy band gap and the decrease of Urbach energy with annealing temperature enhancement. A noticeable sharp absorption band at 748 nm in UV spectra is attributed to A32g(3F)→T31g(3F) electronic transition. Room temperature magnetic hysteresis loops exhibit an increase of saturation magnetization upon annealing which is discussed with reference to finite size effects and disorderly surface spins. The estimated value of magnetocrystalline anisotropy constant by Law of Approach to saturation (LAS) theory as well as coercivity value elucidates the annealing effect in changing the magnetic single domain state of the particle to a multidomain state. Analysis of ZFC and FC magnetization curve measured at 100 Oe in the temperature range 400 K–60 K reveals the significant impact of annealing temperature on magnetic anisotropy, inter-particle interaction, and blocking temperature. Exploring the magnetic hysteresis loop measured in the temperature range 60–400 K over field strength of ± 3 T demonstrates the significant role of annealing on magnetic exchange interaction. Temperature dependent behavior of saturation magnetization and coercivity has been analyzed using modified Bloch's law and Kneller's relation. The magnetic heating efficiency examined by the induction heating system reveals that the sample has enough potential for hyperthermia application.

Comparative heating efficiency of hematite (α-Fe2O3) and nickel ferrite nanoparticles for magnetic hyperthermia application

We report a comparative study of the heating response of hematite (α-Fe2O3) and NiFe2O4 nanoparticles under an alternating magnetic field. In addition, Langevin model and the law of approach to saturation (LAS) are used to confirm the magnetic behavior and to determine the effective anisotropy constant (Keff). Magnetic measurement at room temperature showed superparamagnetic behavior for both samples. This behavior is corroborated by the successfully fitting into Langevin function for paramagnetic materials. We find that α-Fe2O3 nanoparticles has high saturation (2.46 emu/g) compared to the bulk value and Keff (3.12 × 103 erg/cm3), while saturation and Keff for NiFe2O4 nanoparticles are 18.8 emu/g and 2.8 × 104 erg/cm3 respectively. The specific absorption rate (SAR) is investigated under an alternating magnetic field and as a function of concentration (5,10,20 mg/mL) and amplitude of the applied magnetic field (90,130, 170Oe).The SAR and intrinsic loss power (ILP) values obtained for both samples indicated best heating of NiFe2O4 nanoparticles compared to α-Fe2O3 nanoparticles. We showed also that both samples did not reach hyperthermia temperature (42 °C) but maintain a good temperature rise and the SAR values follows linear response theory (LRT). Finally, the contribution of each mechanism in the heat dissipated by α-Fe2O3 and NiFe2O4 nanoparticles were investigated.

Structural and magnetic investigations of innovative lead-free particulate composites of NBT- M-Type SrFe12O19 Hexaferrite

The proposed article enlightens the synthesis, and use of the structural and magnetic properties to evaluate various parameters like lattice constants, residual profile parameters, anisotropy field, and anisotropy constant K1, Mr/Ms ratio, etc. Of (1-x) Na0.5Bi0.5TiO3-(x) SrFe12O19; (x = 0.5, 0.8 and 1) novel composite system formed via solid-state reaction method. Refined parameters throw light on the structural features to examine their effect on the properties of the material. The LAS (Law of approach to saturation) fitting of high field magnetization curves is helpful in calculating the magnetocrystalline-anisotropy field and anisotropy constant. Developed samples accomplish larger Mr/Ms ratio, making them suitable for recording heads and classify their domain structure i.e. multiple domain or single domain, etc. The saturation magnetization obtained for the M-Type strontium Hexaferrite (SM) sample is 77.8 emu/g.

BaSrLaFe12O19 nanorods: optical and magnetic properties

In this work, the Ba0.2Sr0.8−yLayFe12O19 (y = 0.2, 0.4, 0.6 & 0.8) (BSLFO) nanorods were prepared using hydrothermal method. The hexagonal structure and nanorod formation were evidenced by X-ray diffraction patterns and micrographs, respectively. Further, the optical and magnetic properties of the BSLFO nanorods were investigated. Using the UV–Visible spectra of y = 0.2–0.8 contents, the optical bandgap (Eg) was determined. The Eg was increased from 3.502 to 3.714 eV as a function of La content. The Raman modes were detected using the Raman spectra for confirming the hexagonal structure of x = 0.2–0.8. The magnetic hysteresis curve indicated the decreasing trend of saturation magnetization (Ms) from 14.44 ± 0.507 to 4.15 ± 0.162 emu/g with ‘y’. This was determined using the law of approach to saturation (LAS) method. In addition, the magnetic permeability versus temperature (μ′-T) plots showed the decreasing nature of magnetic Curie transition temperature (Tc) from 753 to 703 K with increase of La content. Furthermore, the frequency dependence of magnetic permeability (μ′), magnetic loss (μ″) and relative magnetic loss (rlf: tanδ/μ′) was studied for all samples.

Structural refinement, investigation of dielectric and magnetic properties of NBT doped BaFe12O19 novel composite system

Currently, it is crucial to develop lead-free multifunctional multiferroic composites for lesser environmental hazards, low cost, and diversified potential applications. We have developed a novel lead free ferrite-ferroelectric composite system with composition (1-x)Na0.5Bi0.5TiO3-(x)BaFe12O19; (x = 0.2, 0.5, 0.8 and 1) via solid-state reaction route. The XRD analysis followed by Rietveld Refinement confirmed the formation of hybrid composites with both ferroelectric and ferromagnetic phases. SEM with EDX and HRTEM used to study the morphology and compositional analysis. The slight changes in cell volume, axial ratio (c/a), bond distances and bond angles confirm lattice-distortion. Low frequency and higher temperature dispersion is observed for both dielectric constant and tangent loss. Moreover, dielectric constant increases up to x = 0.5 and then decreases while tangent loss increases with the addition of BaM. The ac conductivity was found to be increased on increasing frequency, temperature and hexaferrite content in the composites. The dc conductivity curve was found to follow the Arrhenius plot. Room temperature multiferroism is confirmed by P-E, M − H loop and magnetoelectric measurements. Anisotropy constant and field were evaluated from fitted high field M − H loop using the law of approach to saturation (LAS) and both of these and other magnetic parameters found to increase with hexaferrite content. It is observed that Ps and Pr increases with BaM up to x = 0.5 and then decreases. The magnetoelectric coupling coefficient is found to show a maximum value of 2.29 mV/cm.Oe for x = 0.2 sample.

Estimation of Magnetic Anisotropy in Ferromagnetic Elements and Their Alloy Powders by the Law of Approach to Saturation (LAS)

Estimation of Magnetic Anisotropy in Ferromagnetic Elements and Their Alloy Powders by the Law of Approach to Saturation (LAS)

The effect of Tb doping on the magnetic properties and microstructure of a TbNdFeCoB/Fe7Co3 nanocomposite permanent magnet

Melt-spun NdFeB-type nanocomposite magnetic materials are important in a number of applications, including electromagnetic sensors, magnetic resonance imaging, and voice coil motors. Herein we investigated the magnetic properties and microstructures of melt-spun TbxNd10−xFe80Co4B6/Fe7Co3 (x = 0.1, 0.2, and 0.3) ribbons by means of x-ray diffractometry, scanning electron microscopy, and magnetization experiments. Tb doping resulted in the formation of a 2:14:1 phase with a higher anisotropy field, which suppressed the separation of Fe7Co3 branch crystals and improved the magnetic properties of the material. Optimum magnetic properties that include a remanence (Jr) of 0.62 T, a coercivity (Hci) of 612.0 kA m−1, and a maximum magnetic energy product ((BH)max) of 94.9 kJ m−3 were obtained for the annealed Tb0.3Nd9.7Fe80Co4B6/Fe7Co3 ribbon. Furthermore, the effective anisotropy constant, and the saturation magnetization, in the nanocomposite were determined by the LATS (law of approach to saturation) method. In this study, the values of and were found to lie between those of hard and soft magnetic phases, consistent with the exchange-coupling concept.

Effect of α-Fe₂O₃ Phase on the Magnetic Interactions in Nickel Ferrite (NiFe₂O₄) Nanoparticles.

We report on the effect of α-Fe₂O₃ phase in the magnetic properties and magnetic interactions in nickel ferrite (NiFe₂O₄-NFO) nanoparticles synthesized by co-precipitation method. Structural analysis confirms the formation of the cubic inverse spinel phase without any impurities for the NFO sample annealed in air at 650 °C. When the annealing temperature is increased to 750 °C and 850 °C, α-Fe₂O₃ impurity phase is formed along with the parent NFO phase. Raman spectra recorded at room temperature (RT) confirm the presence of pure NFO phase for the sample annealed at 650 °C, and presence of α-Fe₂O₃ phase is observed in the samples annealed at 750 °C and 850 °C. Saturation magnetization values at RT for the NFO samples annealed at 650 °C, 750 °C and 850 °C are 34 emu/g, 19 emu/g and 28 emu/g respectively. Zero Field Cooled (ZFC) and Field Cooled (FC) measurement reveals the super-paramagnetic behavior along with competing magnetic interactions in all the samples. For the NFO sample annealed at 750 °C and 850 °C, a drop in ZFC magnetization and a small kink in FC magnetization observed around 245 K indicate the presence of a Morin transition (TM) from the α-Fe₂O₃ phase. Anisotropy constants were calculated for all the samples using the law of approach to saturation (LAS) method. The magnetocrystalline anisotropy energy distribution function for the NFO samples annealed at 750 °C and 850 °C exhibit broad peak due to the random distribution of spins associated with different particle size.

Control of structural and magnetic characteristics of cobalt ferrite by post-calcination mechanical milling

The possibility to control the structural parameters of nanostructured spinel cobalt ferrite paves the way to prepare the ferrite with the anticipated magnetic properties for broad applications. This study is aimed at elucidating the correlation between structural parameters and magnetic properties of cobalt ferrite nanoparticles subjected to post-calcination high-energy ball milling. The milling energy was predicted at four different levels, using the standard collision model. The samples produced were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM). Both FTIR studies and Rietveld refinement of the XRD data shows re-distribution of cations in the spinel structure, induced by a critical level of milling energy. Also, the presence of the three ionization peaks, Co−2p, Fe−2p and O−1s, revealed by XPS confirms the formation of spinel ferrite structure in the cobalt ferrite nanoparticle. The maximum energy products (BH)max of the sample milled under high level ball milling energy was 2.18 MGOe which is almost 5 times higher than that of the un-milled calcined sample. Additionally, the magnetic anisotropy constant was calculated by the Law of Approach to Saturation (LAS) method and indicates a direct correlation between lattice strain and coercivity of samples.