Tang Gui-De

Cation distributions estimated using the magnetic moments of the spinel ferrites Co1?xCrxFe2O4 at 10 K

(A)[B]2O4 ferrite samples with the composition Co1−xCrxFe2O4 (0.0 ≤ x ≤ 1.0) are prepared using a hydrothermal method, and subjected to calcining in atube 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 Fdm. 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 Hunds rules.

Structural and magnetic properties of La0.7Sr0.1AgxMnO3−δ perovskite manganites*

Ag-doped manganite powder samples, La0.7Sr0.1AgxMnO3?? (x = 0.00, 0.025, 0.05, 0.075, and 0.10) were synthesized using the sol?gel method. X-ray diffraction patterns indicated that the samples had two phases with the perovskite being the dominant phase and Mn3O4 being the second phase. X-ray energy dispersive spectra indicated that the ratio of Ag to La was very close to that of the nominal composition in the samples. The specific saturation magnetizations at 300 K increased from 32.0 A?m2/kg when x = 0.00 to 46.8 A?m2/kg when x = 0.10. The Curie temperature, TC, of the samples increased from 310 K when x = 0.00 to 328 K when x = 0.10. Because the atomic concentration ratios of La, Sr, and Mn in the five samples were all the same and only the Ag concentration changed, the variations of the specific saturation magnetizations at 300 K and the Curie temperatures suggested that the Ag cations have been doped into the A sites of the perovskite phase in the samples.

Influence of in-plane field on the stability of vertical Bloch line chains in hard domains of Garnet bubble films

The stability of vertical Bloch line (VBL) chains was statistically studied for all three types of hard domains in garnet bubble films subjected to an in-plane field Hip. With a set of integrate data taken from seven bubble samples and with two typical figures of a sample, four main features of the behavior of VBL chains subjected to Hip were summarized.

Preisach Modelling on the Magnetic Properties of Nano-Particle Fe3O4

A sample of nano-particle Fe3O4 was synthesized using coprecipitation, and characterized by zero field cooling (ZFC) and field cooling (FC) magnetic moments and the major hysteresis loops. The data are analysed within the framework of a generalized Preisach model, which provides an excellent description of the experimental data. The simulated results are in good agreement with the experimental data. Using the model, we obtain that the blocking temperature of Fe3O4 nano-particles with diameter of 8.4 nm is 105 K, and the interaction field distribution between the particles is 550 Oe.

Self-collapse of Dumbbell Domains in Garnet Bubble Films

The self-collapse phenomenon of dumbbell domains was studied experimentally. The coincidence of the bias field region of self-collapse with that of collapse for both the first and second kinds of dumbbells manifests that two necessary conditions for self-collapse are: (1) sufficiently high number of vertical Bloch lines (VBLs) in their walls and (2) these VBLs are in high compression, and there exists the similarity between self-collapse and collapse in mechanism.