Spin-glass and reentrant spin-glass states in iron sulfospinels having dilute A and B sublattices

Abstract

The magnetic and electrical properties of new compounds having spinel structure Fe1−xCr2(1−x)Sn2xS4 (0.1⩽x⩽0.33) (system 1), Fe0.67 [Fe0.165CrSn0.835]S4, and Fe0.67 [Fe0.33Cr0.67Sn]S4 has been studied. These compounds are p-type semiconductors with magnetic properties characteristic of the following magnetic-order types: ferrimagnetic (the x=0.1 composition of system 1), spin glass (the x=0.33 composition of system 1 and Fe0.67 [Fe0.165CrSn0.835]S4), and reentrant spin glass (the x=0.2 composition of system 1 and Fe0.67 [Fe0.33Cr0.67Sn]S4). For the spin-glass compositions, the dependence of the freezing temperature Tf defined as the temperature of the maximum of initial magnetic susceptibility, on temperature and magnetic field obeys the Almeida-Thouless relation, and the dependence of Tf on magnetic-field frequency is a power-law function. For the spin-glass and reentrant spin-glass compositions, a large peak in the absolute value of negative isotropic magnetoresistance was found near Tf, which becomes as high as 15% in spin glasses and 30% in reentrant spin-glass compositions. In compositions with reentrant behavior, the activation energy of conductivity in the region of Tf was found to change by about two orders of magnitude. This experimental evidence suggests that the spin-glass-paramagnet (in spin glasses) and spin-glass-long-range magnetic-order transformations are actually phase transitions, and that the spin-glass region contains ferron-type ferromagnetic clusters. These are the first spin-glasses among the chalcospinels with magnetically active ions on the tetrahedral and octahedral sublattices.