Cation distribution and magnetic properties of ternary spinels

Abstract

The series of spinels was prepared by ceramic technology. The crystal structures were refined from the x-ray diffraction data using the Rietveld profile method. The high-temperature magnetic susceptibility was measured by the Faraday method in the temperature range 290 - 600 K and the data were fitted to the Curie - Weiss law. The cation distribution in these diluted magnetics is obtained from x-ray diffraction and high-temperature magnetic susceptibility measurements. It was found that, for , ions occupy exclusively the octahedral position in the spinel type of structure. In the low-concentration region a strong clustering of magnetic ions is observed. In the range , ions are distributed in both tetrahedral and octahedral cationic sites. The Curie - Weiss paramagnetic temperature is negative in the whole range of concentrations, as the consequence of a predominant antiferromagnetic interaction. The appearance of the ions in tetrahedral sites (around x = 1.33) leads to a drop in the absolute -value. The effective magnetic moments of ions are about for and depend on the concentration for x>1.33.

Cation distribution and crystallographic characterization of the quaternary spinel system Mg Co1−Cr Fe2−O4

“…The knowledge of the crystallography including the cation distribution is thus very important for controlling and forecasting the various properties in spinels. In view of that, the crystallography including site preferences of cations in spinels have been systematized intensively and increasing emphasis are given on the exact cation distributions in complex systems [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In the present work we report crystallographic characterization and the cation distribution in the spinel system Mg x Co 1−x Cr x Fe 2−x O 4 (x = 0.0, 0.25, 0.50, 0.75 and 1.0) consisting of four different cations of which Co, Fe and Cr have close atomic numbers.…”

Grain boundary electric characterization of Zn7Sb2O12 semiconducting ceramic: A negative temperature coefficient thermistor

“…This oxide has received small attention, despite its great potential for application in the advanced materials area, such as ceramic pigment, 2 microstructure controller in ZnO-based varistors, 3 polycrystalline semiconductors 4 and magnetic materials. 5 Currently, the most important set of physical and chemical data on Zn 7 Sb 2 O 12 is correlated to ZnO-based varistors, a typical electroceramic device with a highly nonlinear voltage-current characteristic. 6 A nonlinear relation between voltage and current at lowfield applications has been reported for Zn 7 Sb 2 O 12 ceramics synthesized via a chemical route.…”

A practical approach to Rietveld analysis. Comparison of some programs running on personal computers

“…The spinel with overall composition (Zn)[Zn 0 400 Ni 0 9 33 Sb 0 667 ]O 4 was chosen for this study because of its cubic symmetry and high degree of crystallinity. This compound was previously prepared for the investigation of structural and magnetic properties of some complex spinels with general formula Zn^MySKC^ (Poleti et al, 1994;Ilic et al, 1996). The sample preparation and cation distribution are described in the cited papers.…”