Hydrothermal Synthesis,Structural and Electrical Properties of Antimony (Sb3+) Substituted Nickel Ferrites

Antimony (Sb³⁺) doped nickel ferrites have been synthesized by hydrothermal route using an autoclave at 160 ^°C for 12 hours. Pure spinel phase NiSb _x Fe_2?x O₄ (x=0.0 to 0.1) with step increment of 0.035 has been prepared by sintering the precursor samples at 500 ^°C. Structural studies have been performed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Lattice parameter and X-ray density found to increase with increase in the antimony concentration. Average crystallite size lies in the range of 14 to 24 nm?±?2 nm. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) have been used to characterize the morphology and sizes of nanoparticles. Electrical properties were analyzed by measuring DC-electrical resistivity, complex dielectric permittivity, AC conductivity and complex electrical modulus analysis. DC resistivity of nickel ferrites decreases due to the substitution of antimony from 6.7×10⁸ to 3.4×10⁷ Ω-cm. Dielectric permittivity and losses were studied in the frequency range of 20 Hz–5 MHz and found to increase due to addition of Sb³⁺ in nickel nanoferrites at room temperature. High dielectric permittivity and conductivity made this material a compatible option for single-layered and multilayered chip inductors.     

Studies on the Properties of Manganese Substituted Nickel Ferrite Nanoparticles

Mn²⁺-substituted Ni ferrite nanoparticles were synthesized by sol-gel auto combustion method. The synthesized samples were annealed at 800 ^°C and characterization studies were carried out by XRD, VSM, electron paramagnetic resonance (EPR), field emission scanning electron microscopy (FE-SEM) and FT-IR spectroscopy. The XRD patterns revealed that Mn ²⁺-substituted Ni ferrite crystallizes in cubic spinel phase and addition of α-Fe ₂ O ₃ phase was also observed. The average crystallite sizes were found to be from 42 to 56 nm using a Scherer equation. The coercivity and remanent magnetization decreases when Mn ²⁺ ion concentration is increased. The EPR spectrum shows the phase homogeneity of the samples. The FE-SEM images revealed that particles are both spherical in shape and particle sizes varied from 22 to 41 nm. The FT-IR spectrum confirmed the two main metal ion vibrations of nickel ferrite near 550 to 560 cm ^?1 (A site) and 441 to 460 cm ^?1 (B site).     

Structural,Magnetic, Optical and Electrical Properties of Ba Substituted BiFeO3

Ba²⁺ substituted bismuth ferrite (BFO) (Bi_1?x Ba _x FeO₃, x=0, 0.1, 0.2, and 0.3) was prepared by chemical route using nitrates as a precursor, and sintered at 830 °C for 1 hr. The structural, optical, magnetic, and electrical properties of the prepared samples were investigated to understand the effect of Ba²⁺ substitution in BFO. The samples were characterized by X-ray diffraction (XRD), and shows an impurity phase which reduces drastically on substitution. Magnetic measurements were carried out at room temperature up to a field of 20 kOe. Magnetic hysteresis loops revealed a significant change in magnetization on Ba²⁺ substitution in BFO with unsaturated nature. Further, the Fourier transformed Infrared (FTIR) and Ultra Violet Visible (U-V Vis) spectra of the samples at room temperature shows as a change in spectral behavior on substitution. The AC electrical conductivity analyzed through Impedance analyser at different temperatures and frequencies. The ac conductivity and its activation energies for the samples are found to be frequency and temperature dependent and also vary with Ba²⁺ substitution in BFO.     

Effect of Ni Content on Structural and Magnetic Properties of Li-Ni Ferrites Nanostructure Prepared by Hydrothermal Method

Li-Ni ferrite with chemical formula Li_0.5?0.5x Ni _x Fe_2.5?0.5x O₄ was prepared by hydrothermal method with different Ni contents (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) using metal chlorides, ferrous sulfate and sodium hydroxide as oxidants. The hydrothermal treatment was accomplished at (155 ^° C) for (3 h). The required analyses of XRD, FTIR, SEM, TEM, EDX and magnetic hysteresis loop were performed to characterize the complete behavior as a function of x. It was found that lattice constant has a small increase as x increased. Crystallite size had a minimum value of about 13 nm at x = 1.0 and maximum value of about 33 nm at x = 0.3. It was also found that XRD density increased as x was increased. The particle size distributions showed that the maximum value is around 22 nm. FTIR analysis showed the presence of two main peaks with some shifting. Nanospheres were the predominant particles beside the presence of low nanorod concentration. M-H loops had super paramagnetic shape. The coercivity had a minimum value at x = 0.5. The magnetic saturation had a maximum value at x = 0.3, and the initial susceptibility χ _i had a maximum value at x = 0.5.     

Structural and Magnetic Properties of Cobalt and Copper Ions Mixed Nickel Ferrite Nanoparticles

Co²⁺ and Cu²⁺ ions mixed nickel ferrite nanoparticles were synthesized by sol-gel auto combustion method. XRD patterns revealed the existence of a single-phase cubic spinel structure. The average grain size estimated from XRD patterns was found to be from 42 to 56 nm. VSM study indicates increase in saturation magnetization and decrease in coercivity. FE-SEM images exhibit particles with spherical shape and size ranges from 37 to 79 nm. The two main metal ion vibrations of ferrites were observed in FT-IR spectra.     

Structural, Magnetic, and Optical Properties of Zinc- and Copper-Substituted Nickel Ferrite Nanocrystals

Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add non-magnetic dopants Zn and Cu to nickel ferrite nanocrystals, Ni_1?x M _x Fe₂O₄ (0??x??1, M=Cu, Zn), and study how relevant properties of the samples are modified accordingly. Basically, these dopings cause a rearrangement of Fe⁺³ ions into the two preexisting octahedral and tetrahedral sites. In fact, this, we show, induces pertinent magnetic properties of the doped samples. In the case of the Cu-doping, the Jahn?CTeller effect also emerges, which we identify through the Fourier Transform Infra-Red Spectroscopy of the samples. Moreover, we show an increase in the lattice parameters of the doped samples, as well a superparamagnetic behavior for the doped samples is shown, while the Jahn?CTeller effect precludes a similar behavior in the CuFe₂O₄ nanocrystals. The influences of Zn and Cu substitutions are investigated on the optical properties of nickel ferrite nanocrystals by photoluminescence measurement at room temperature.     

High-Frequency Tunneling Magnetic Loss in Soft Ferrites

This paper considers high-frequency (200 kHz-1.0 MHz) losses in MnZn power ferrites and shows that none of the three well-known magnetic loss mechanisms (namely, hysteresis, classical eddy-current loss, and excess eddy-current loss) can account for the experimentally observed dependence of the loss on the frequency and flux density. In order to investigate the origin of this discrepancy, the electric field that is induced in the typical core when the material is driven at high frequencies and flux densities was estimated. The estimates show that these electric fields can be quite large. The paper presents experimental data on the electrical conductivity for such large electric fields, which shows a highly nonlinear behavior that can give rise to a modified eddy-current loss mechanism. By a simple curve fit to the nonlinear conductivity, the experimentally observed flux density dependence of the high-frequency loss, which previously could not be explained, can be reproduced by using this modified eddy-current loss mechanism. A modified ferrite structure can eliminate most of these extra losses by reducing the electric field generated at the grain boundaries due to high frequencies and flux densities     

Magnetic Characteristics of a Nanocomposite Based on Bismuth Ferrites

Technical Physics Letters - The magnetization process in the nanocomposite BiFeO3–Bi2Fe4O9 obtained by the glycine–nitrate combustion, was studied. The magnetic characteristics of the...     

CuO对LiZn铁氧体微观结构和磁性能的影响

采用氧化物陶瓷工艺在1000～1160℃制备掺CuO的LiZn铁氧体Li0.35Zn0.3Fe2.35O4.结果表明,在1000～1100℃烧结时适量的CuO可促进固相反应和晶粒生长,降低烧结温度,提高样品的密度、饱和磁化强度4πMs和剩磁Br,降低矫顽力Hc.在1130℃烧结时,CuO基本无助烧作用,且增加CuO含量出现异常晶粒长大现象.在1160℃烧结时,样品内部形成巨晶,虽有利于降低Hc,但导致Br明显下降.     

Electronic and Magnetic Investigations of Rare-Earth Tm-doped AlGaN Ternary Alloy

Electronic structure and magnetic interaction of substitutional thulium rare earth-doped wurtzite Al_0.5Ga_0.5N ternary alloy have been performed using density-functional theory within local spin-density approximation with Hubbard-U corrections (LSDA+U) approach. The LSDA+U method is applied to the rare earth (RE) 4f states. The calculation of formation energy shows that it is more energetically favorable for a substitutional Tm atom to replace the Al atom than the Ga atom. For AlGaN:Tm, the lattices parameters are expanded due to larger ionic radius of Tm than that of Al atoms. The energy band gap of AlGaN:Tm has direct character and its width becomes small compared with that of AlGaN. The magnetic coupling between Tm ions in the nearest neighbor sites is ferromagnetic. Magnetic interaction of rare earth ion with the host states at the valence and conduction band edges has been investigated and compared to those of GaN:Mn and has been found to be relatively small.     

Complex Magnetic Permeability and Dielectric Permittivity of Ferrites in Millimeter Waves

We report a first-time study of complex magnetic permeability and dielectric permittivity of 99% pure powdered barium cobalt ferrite (Ba₂Co₂Fe₁₂O₂₂) and pure solid barium hexaferrite ceramics (BaFe₁₂O₁₉) in a broadband millimeter-wave frequency range. We performed transmittance measurements using a free-space quasi-optical millimeter-wave spectrometer, equipped with a set of high-power backward-wave oscillators as sources of tunable coherent radiation at each Q-, V-, and W-frequency band. We calculated frequency dependences of complex permittivity for both types of ferrites using analysis of recorded high-precision transmittance spectra and obtained frequency dependences of the magnetic permeability from Schlomann's equation for partially magnetized ferrites.     

Study of Magnetic Phase Transition in Diluted Nanostructure Spinel Ferrites

The magnetic properties of CoFe_2−2x Cr_2x O₄ spinels are studied by different theoretical methods: the mean field theory, the high-temperature series expansions (MFT, HTSE) and the probability distribution law with the different size L (nm). The exchange interactions and the critical temperature T _c (K) are given for the nano-spinel ferrites. The magnetic phase diagram of CoFe_2−2x Cr_2x O₄ is deduced. The saturation magnetization, the coercivity field and magnetic energy are obtained.     

Structural and Magnetic Properties of Nano-structured Eu 3+ Substituted M-Type Hexaferrites Synthesized by Sol-Gel Auto-combustion Technique

Nano-structured M-type hexaferrites having the nominal composition Sr_0.8Ca_0.2Eu _x Fe_12?x O₁₉ (x=0.0, 0.05, 0.1, 0.15, 0.2, 0.25) have been synthesized by a sol-gel auto-combustion technique. The aim of the present study is to investigate the effect of rare-earth Eu³⁺ ions substitution at Fe³⁺ site on the structural and magnetic properties of M-type hexaferrites that might have not been previously explored especially using the sol-gel auto-combustion technique. The samples have been characterized by Differential Scanning Calorimetry (DSC), Fourier Transform Infra-Red (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (ED-XRF) and vibrating sample magnetometer (VSM). The XRD analysis confirms the formation of single M-type hexaferrite phase. The ratio ‘c/a’ lies in the expected range of 3.946–3.951 for M-type hexaferrites phase. The crystallite size was found to be in the range of 15–45 nm, which is sufficient to obtain the suitable signal to noise ratio in the high density recording media. Scanning Electron Microscopy (SEM) analysis exhibits the morphology of grains to be hexagonal platelet. The values of remanence (M _r ) and maximum magnetization (M) lie in the range 31–68 emu/g and 47–90 emu/g, respectively. The coercivity (H _c ) values lie in the range of 2412–4046 Oe and enhancement in the coercivity may be due to increase in the shape anisotropy. The magnetic properties such as coercivity (H _c ), magnetization (M), and retentivity (M _r ) make the synthesized materials useful for applications in the recording media.     

Magnetic and Structural Properties of Ni/NiO Nanoparticles Prepared Using Nickel Acetate and Polyvinyl Acetate Precursor

Ni/NiO nanoparticles were synthesized using a mixture of nickel acetate and polyvinyl acetate as precursors, followed by heating between 350–450 °C. The prepared samples were investigated using XRD, TEM and SQUID magnetometry. Depending on the heating temperature, the average sizes of Ni and NiO crystallites were found to be in the ranges of 25–37 nm and 10–26 nm, respectively. The analysis of XRD patterns shows that the volume percentage of Ni can be easily controlled by the heating temperature. Magnetization measurements show that the samples consist of ferromagnetic moments which are blocked at low temperatures and a disordered NiO component which causes spin-glass like behavior.     

Measurement and Modeling of Thermal Effects on Magnetic Hysteresis of Soft Ferrites

We present experimental measurement of thermal effects on magnetic hysteresis of soft ferrite cores commonly used in high-frequency inductors and transformers and propose a method to model the thermal effects. We measured the major hysteresis loops of soft ferrite core samples from various vendors at different temperatures, and found that the saturation points of the limiting hysteresis loops vary with the temperature substantially in a nonlinear manner, but within the normal operating temperature range, typically 20degC-100degC, this variation can be approximately regarded as linear with an acceptable error. We propose a simple method based on this approximation for determining the limiting hysteresis loop of a soft ferrite for a given temperature. This method is validated by the substantial agreement between the experimental measurement and simulation by the scalar Preisach hysteresis model of major hysteresis loops of the test samples at different temperatures. Since most manufacturers provide the limiting loops of their soft ferrite cores at two typical temperatures, the proposed method is very convenient for engineering applications.     

添加剂粒度细化对锶铁氧体结构和磁性能的影响

研究了添加剂粒度对锶铁氧体永磁材料结构和磁性能的影响.结果表明,添加剂粒度的细化使锶铁氧体的晶粒细化,提高了磁性相的取向度,改善了磁体的综合磁性能,特别是显著改善了剩磁和最大磁能积.添加剂粒度的细化使烧结温度对磁性能的影响更敏感,降低了最佳烧结温度,有利于实现低能耗下高性能产品的生产.