（A）[B]2O4 ferrite samples with the composition COl_xCrxFe204 （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 diff...（A）[B]2O4 ferrite samples with the composition COl_xCrxFe204 （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 Fd3m. 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 l 0 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
Eased on four constant parameters (the site energy differences E-M2-E-M1 = 25.50 kJ/mol, E-M3-E-M1 = -10.73 kJ/mol and the potential energies of interactions between the cation pairs occupying adjacent sites W-12 = 45...Eased on four constant parameters (the site energy differences E-M2-E-M1 = 25.50 kJ/mol, E-M3-E-M1 = -10.73 kJ/mol and the potential energies of interactions between the cation pairs occupying adjacent sites W-12 = 45.60 kJ/mol W-14 = 0.56 kJ/mol) and a temperature-dependent parameter E-M4-E-M1 = 2.68(T/323)(2.5) kJ/mol, the equilibrium distributions of the exchangeable cations, K-s(+,), over those four available cation sites in K22.4Al22.4Si73.6O192 are studied by the simulated annealing method.展开更多
A series of polycrystalline samples of Co_(1-x)Zn_(x)Fe_(2)O_(4)where(x=0.1,0.2,0.3,0.4,0.5 and 0.6)were prepared by the usual ceramic technique.X-ray diffraction patterns confirmed the spinel cubic structure.The diff...A series of polycrystalline samples of Co_(1-x)Zn_(x)Fe_(2)O_(4)where(x=0.1,0.2,0.3,0.4,0.5 and 0.6)were prepared by the usual ceramic technique.X-ray diffraction patterns confirmed the spinel cubic structure.The diffusion coefficients of oxygen vacancies were estimated from dc conductivity measurements.It was noticed that the diffusion coefficient decreases with increasing Zn^(2+)concentrations.An increase of temperature increases the diffusion of lattice vacancies.The Curie temperature,lattice parameter and jump length of electrons were studied as a function of Zn^(2+)concentration.From the correlation between the ionic radius and the radii of octahedral and tetrahedral sites,the theoretical lattice parameters were calculated and suggested cation distribution for the given ferrites was determined.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]2O4 ferrite samples with the composition COl_xCrxFe204 （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 Fd3m. 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 l 0 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.
文摘Eased on four constant parameters (the site energy differences E-M2-E-M1 = 25.50 kJ/mol, E-M3-E-M1 = -10.73 kJ/mol and the potential energies of interactions between the cation pairs occupying adjacent sites W-12 = 45.60 kJ/mol W-14 = 0.56 kJ/mol) and a temperature-dependent parameter E-M4-E-M1 = 2.68(T/323)(2.5) kJ/mol, the equilibrium distributions of the exchangeable cations, K-s(+,), over those four available cation sites in K22.4Al22.4Si73.6O192 are studied by the simulated annealing method.
文摘A series of polycrystalline samples of Co_(1-x)Zn_(x)Fe_(2)O_(4)where(x=0.1,0.2,0.3,0.4,0.5 and 0.6)were prepared by the usual ceramic technique.X-ray diffraction patterns confirmed the spinel cubic structure.The diffusion coefficients of oxygen vacancies were estimated from dc conductivity measurements.It was noticed that the diffusion coefficient decreases with increasing Zn^(2+)concentrations.An increase of temperature increases the diffusion of lattice vacancies.The Curie temperature,lattice parameter and jump length of electrons were studied as a function of Zn^(2+)concentration.From the correlation between the ionic radius and the radii of octahedral and tetrahedral sites,the theoretical lattice parameters were calculated and suggested cation distribution for the given ferrites was determined.
