(A)[B]2O4ferrite samples with the composition Co1-xCrxFe2O4(0.0 ≤ x ≤ 1.0) are prepared using a hydrothermal method, and subjected to calcining in a tube furnace with an argon-flow at 1673 K for 2 h. X-ray diffracti...(A)[B]2O4ferrite samples with the composition Co1-xCrxFe2O4(0.0 ≤ x ≤ 1.0) are prepared using a hydrothermal method, and subjected to calcining in a tube furnace with an argon-flow at 1673 K for 2 h. X-ray diffraction patterns indicate that each of all the samples has a single phase cubic spinel structure with a space group of Fdˉ3m. Magnetic measurements show that the saturation magnetization decreases with as the Cr content x increases. The cation distribution of the samples is estimated by fitting the dependence of the magnetic moments on x at 10 K, using the quantum mechanical model previously proposed by our group. The calculated sum of the content values of the Cr3+and Cr2+cations occupying the(A) sites increases as the value of x increases. In the fitting process, the magnetic moment directions of the Cr3+and Cr2+cations are assumed to be antiparallel to those of the Fe and Co cations, respectively, which is in accordance with Hund's rules.展开更多
In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co0.5Ni0.5-xMgxFe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological ...In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co0.5Ni0.5-xMgxFe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co–Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction（XRD） analysis, Fourier transform infrared spectroscopy（FTIR）, field emission scanning electron microscopy（FESEM）, and vibrating sample magnetometry（VSM）. The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of 32 nm to 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from 57.35 emu/g to 61.49 emu/g and 603.26 Oe to 684.11 Oe（1 Oe = 79.5775 A·m-1）, respectively. The higher values of magnetization Ms and Mr suggest that the optimum composition is Co0.5Ni0.4Mg0.1Fe2O4 that can be applied to high-density recording media and microwave devices.展开更多
The Ni1–xCuxFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) ferrites have been prepared by sol-gel method in order to obtain homogeneous crystal structure and they are sintered at high temperature. ...The Ni1–xCuxFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) ferrites have been prepared by sol-gel method in order to obtain homogeneous crystal structure and they are sintered at high temperature. The effect of copper doping on the structural and magnetic properties of nickel ferrites sintered at 1000°C has been examined. The X-ray diffraction measurements clearly showed the formation of single phase spinel ferrite structure in all the prepared ferrite compositions. Because of the high sintering temperature the particle size is observed beyond the nano-scale range in all the compositions. The lattice parameters are found to increase with increasing doping concentration of the copper content. Magnetization results exhibit a non-collinear ferrimagnetic structure for x = 0.0 to 0.5 and Neel’s collinear ferrimagnetic structure for x = 0.5 to 0.9 suggesting a change in magnetic ordering.展开更多
The magnetic,conductivity,and dielectric properties have been investigated in single-phase polycrystalline Y0.1 Co1.9 MnO4.The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a lo...The magnetic,conductivity,and dielectric properties have been investigated in single-phase polycrystalline Y0.1 Co1.9 MnO4.The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a low temperature (～186 K).Magnetisation as a function of field H (M-H loop) indicated the weak ferromagnetism of the sample at room temperature.The constant ε and dielectric loss tgδ measurements represent a ferroelectric phase transition at a higher temperature (～650 K),while the conductivity shows an insulator-metallic transition.The ferroelectric hysterisis loops and capacitance-voltage measurements confirm the ferroelectric nature of the sample at room temperature.The observed ferromagnetism and ferroelectric nature in this material suggests a potential multiferroic application.展开更多
The polycrystalline MgCrxFe2-xO4 ferrites (0.0 ? x ? 1.0) were prepared by conventional solid state ceramic sintering technique in air at 1300?C. X-ray diffraction experiments were carried out on all the samples in or...The polycrystalline MgCrxFe2-xO4 ferrites (0.0 ? x ? 1.0) were prepared by conventional solid state ceramic sintering technique in air at 1300?C. X-ray diffraction experiments were carried out on all the samples in order to characterize the materials at room temperature. The X-ray diffraction patterns showed sharp peaks indicating the formation of single phased cubic spinel structure. The lattice parameters of the samples were determined from the X-ray diffraction data using Nelson-Riley extrapolation method. It was found that the lattice parameter decreased with increasing Cr concen- tration obeying Vegard’s law. Magnetic properties of the samples were measured using an Impedance Analyzer. Real and imaginary parts of the complex permeability, loss factor and quality factor were measured as the function of frequency at three different sintering temperatures 1250?C, 1300?C and 1350?C for all the samples in the frequency range 1 kHz to 13 MHz. Frequency stability of the real part of permeability increases with increasing Cr concentration and also with sintering temperature. Imaginary part of permeability decreases with increasing frequency and increased with increasing both of the Cr content and sintering temperature. Loss factor decreased with increasing frequency while the quality factor (Q) increased with increasing frequency for all the samples. The temperature de- pendence of initial permeability was measured for all the samples sintered at 1300?C. The Curie temperature (Tc) was determined from the -T curves. The values of Tc were found to be 733 K, 657 K, 583 K, 468 K, 400 K and 317 K for x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, respectively.展开更多
The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Car...The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.NSF-11174069)the Natural Science Foundation of Hebei Province,China(Grant No.E2011205083)+1 种基金the Key Item Science Foundation of the Education Department of Hebei Province,China(Grant No.ZD2010129)the Young Scholar Science Foundation of the Education Department of Hebei Province,China(Grant No.QN20131008)
文摘(A)[B]2O4ferrite samples with the composition Co1-xCrxFe2O4(0.0 ≤ x ≤ 1.0) are prepared using a hydrothermal method, and subjected to calcining in a tube furnace with an argon-flow at 1673 K for 2 h. X-ray diffraction patterns indicate that each of all the samples has a single phase cubic spinel structure with a space group of Fdˉ3m. Magnetic measurements show that the saturation magnetization decreases with as the Cr content x increases. The cation distribution of the samples is estimated by fitting the dependence of the magnetic moments on x at 10 K, using the quantum mechanical model previously proposed by our group. The calculated sum of the content values of the Cr3+and Cr2+cations occupying the(A) sites increases as the value of x increases. In the fitting process, the magnetic moment directions of the Cr3+and Cr2+cations are assumed to be antiparallel to those of the Fe and Co cations, respectively, which is in accordance with Hund's rules.
基金supported by the Ibnu Sina Institute for Scientific and Industrial Research,Physics Department of Universiti Teknologi Malaysia and the Ministry of Education Malaysia(Grant Nos.Q.J130000.2526.04H65)
文摘In this study, nanocrystalline Co–Ni–Mg ferrite powders with composition Co0.5Ni0.5-xMgxFe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co–Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction（XRD） analysis, Fourier transform infrared spectroscopy（FTIR）, field emission scanning electron microscopy（FESEM）, and vibrating sample magnetometry（VSM）. The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of 32 nm to 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from 57.35 emu/g to 61.49 emu/g and 603.26 Oe to 684.11 Oe（1 Oe = 79.5775 A·m-1）, respectively. The higher values of magnetization Ms and Mr suggest that the optimum composition is Co0.5Ni0.4Mg0.1Fe2O4 that can be applied to high-density recording media and microwave devices.
文摘The Ni1–xCuxFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) ferrites have been prepared by sol-gel method in order to obtain homogeneous crystal structure and they are sintered at high temperature. The effect of copper doping on the structural and magnetic properties of nickel ferrites sintered at 1000°C has been examined. The X-ray diffraction measurements clearly showed the formation of single phase spinel ferrite structure in all the prepared ferrite compositions. Because of the high sintering temperature the particle size is observed beyond the nano-scale range in all the compositions. The lattice parameters are found to increase with increasing doping concentration of the copper content. Magnetization results exhibit a non-collinear ferrimagnetic structure for x = 0.0 to 0.5 and Neel’s collinear ferrimagnetic structure for x = 0.5 to 0.9 suggesting a change in magnetic ordering.
基金supported by the Doctorial Start-up Fund of Guizhou University of China (Grant No. 2006/Z065020)
文摘The magnetic,conductivity,and dielectric properties have been investigated in single-phase polycrystalline Y0.1 Co1.9 MnO4.The temperature-dependent magnetisation reveals the ferromagnetic transition in sample at a low temperature (～186 K).Magnetisation as a function of field H (M-H loop) indicated the weak ferromagnetism of the sample at room temperature.The constant ε and dielectric loss tgδ measurements represent a ferroelectric phase transition at a higher temperature (～650 K),while the conductivity shows an insulator-metallic transition.The ferroelectric hysterisis loops and capacitance-voltage measurements confirm the ferroelectric nature of the sample at room temperature.The observed ferromagnetism and ferroelectric nature in this material suggests a potential multiferroic application.
文摘The polycrystalline MgCrxFe2-xO4 ferrites (0.0 ? x ? 1.0) were prepared by conventional solid state ceramic sintering technique in air at 1300?C. X-ray diffraction experiments were carried out on all the samples in order to characterize the materials at room temperature. The X-ray diffraction patterns showed sharp peaks indicating the formation of single phased cubic spinel structure. The lattice parameters of the samples were determined from the X-ray diffraction data using Nelson-Riley extrapolation method. It was found that the lattice parameter decreased with increasing Cr concen- tration obeying Vegard’s law. Magnetic properties of the samples were measured using an Impedance Analyzer. Real and imaginary parts of the complex permeability, loss factor and quality factor were measured as the function of frequency at three different sintering temperatures 1250?C, 1300?C and 1350?C for all the samples in the frequency range 1 kHz to 13 MHz. Frequency stability of the real part of permeability increases with increasing Cr concentration and also with sintering temperature. Imaginary part of permeability decreases with increasing frequency and increased with increasing both of the Cr content and sintering temperature. Loss factor decreased with increasing frequency while the quality factor (Q) increased with increasing frequency for all the samples. The temperature de- pendence of initial permeability was measured for all the samples sintered at 1300?C. The Curie temperature (Tc) was determined from the -T curves. The values of Tc were found to be 733 K, 657 K, 583 K, 468 K, 400 K and 317 K for x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, respectively.
文摘The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.
