D.L. Hou

Magnetic anisotropy and coercivity of ultrafine iron particles

Abstract Ultrafine iron particles are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Using the law of approach to saturation (LATS), effective magnetic anisotropy is obtained at different temperatures. K E increases with the decrease of temperature, and decreases with the thickening of the surface oxide layer. The temperature dependence of coercivity has been investigated.

Influence of preparing condition on magnetic properties of the FeCoNi–SiO2 granular alloy solids

Abstract FeCoNi–SiO 2 granular alloy solids have been prepared using a sol–gel method, and investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The influences of the preparing condition and the alloy concentration on the magnetic properties have been thoroughly studied. The dependences of the magnetic properties and the lattice constant of FeCoNi alloy particles on the Ni content have been discussed.

Oxygen content and magnetic properties of composites La0.75Sr0.25MnO3±δ calcined at different temperatures

The effects of the calcination temperature on the oxygen content and magnetic properties of the nanocrystalline perovskite manganite La0.75Sr0.25MnO3±δ prepared by the sol–gel method were investigated. The highest temperatures at which the samples were calcined were 973, 1073, 1273, and 1473xa0K. The X-ray diffraction (XRD) analyses indicate that all the samples have only a single phase with the

Preparation and magnetic properties of Fe0.7Co0.3-SiO2 granular alloy solid

Rbar{3}c

Enhancing the Thermoelectric Properties of Ca3Co4O9 Thin Films by the Addition of a Nanoscale NbNx Second Phase

R3¯c perovskite structure. As the calcination temperature and calcination time increase, the oxygen content in the samples increases from being deficient to being in excess of that in the stoichiometric formula. The crystallite size also increases from 23 to 283xa0nm. Magnetic measurements indicate that the sample calcined at 1073xa0K has the highest Curie temperature. This is owing to the fact that the crystallite cores of this sample have stoichiometric oxygen content. The dependence of the Curie temperature and the saturation magnetization on the calcination temperature are successfully explained.

Magnetic properties of Ga doped NdFeCoB sintered magnets

The granular γ-Fe 2 O 3 powders are prepared. The particle shapes and mean particle sizes of the samples are determined by Transinission Electron Microscopy (TEM). Using Extracting Sample Magnetometer (ESM) and Vibrating Sample Magnetometer (VSM), the magnetic parameters are measured at different temperatures. By the Law of Approach to Saturation (LATS), the effective magnetic anisotropy constants K E of granular γ-Fe 2 O 3 powders at different temperatures are obtained. By using the mixed-coercivity model, a good explanation is given to the temperature dependence of the coercivity for granular γ-Fe 2 O 3 . It is found experimentally, for the first time, that the variation tendency of K E with temperature for granular γ-Fe 2 O 3 is about the same as that of the shape magnetic anisotropy K sh and that the magnetization reversal process of granular γ-Fe 2 O 3 is close to uniform rotation at different temperatures.

Studies on the magnetic viscosity and the magnetic anisotropy of γ-Fe2O3 powders

The Fe 0.7 Co 0.3 -SiO 2 granular alloy solid has been prepared using a sol-gel method, and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The effective magnetic anisotropy K E has been measured by the law of approach to saturation (LATS). The evolution of the magnetic properties for the granular alloy solid during reducing is described and explained by means of particle size distribution and superparamagnetic behaviour. When the measuring temperature changes from 100 to 800 K, the variations of saturation magnetization, effective magnetic anisotropy and coercivity of the Fe 0.7 Co 0.3 -SiO 2 granular solid are much smaller than those of existing magnetic recording media. The Fe 0.7 Co 0.3 -SiO 2 granular alloy solid has a potential for application in high density magnetic recording media, which can be used in a wide temperature range.

Temperature stability and linear magnetic field response of the magnetoresistance in Ag0.07–La0.67Sr0.13Ag0.08Ä0.12MnO3 composite

The temperature dependence of the coercive field (H/sub c/) and the thermal fluctuation field (H/sub f/) of Nd-Fe-B sintered magnets was measured from 100 K to 500 K. It was found that a linear relationship exists between l/sub g/H/sub f/ and l/sub g/H/sub c/ in this temperature range. The relationship between l/sub g/H/sub c/ and l/sub g/H/sub f/ was deduced from Gaunts localized weak pinning model. Values of l/sub g/H/sub c/ calculated from the derived relationship are in very good agreement with experimental values. >