Magnetic properties of the reentrant spin glass FeCr2xIn2-2xS4

Mossbauer spectroscopy, and magnetization measurements were performed on Fe Cr2xIn2-2xS4 ceramic samples with x = 0.1 and 0.3. Mossbauer hyperfine para meters indicate that iron is in a Fe2+ state, with major population at octa hedral B sites and similar to 10% of Fe2+ at A sites of the spinel stnlctur e. Low-field DC magnetization data shows a sharp onset of the magnetic orde r at T-C = 156(1) K. Below this temperature, field-cooled (FC) and zero-fie ld-cooled (ZFC) curves display strong irreversibility. The irreversibility decreases with increasing applied magnetic field. Reentrant spin-glass tran sition is observed at T-sg = 9.0(1) It, which shifts to lower T and broaden s with applied field. From AC data at different driving frequencies f, it i s found that the frequency shift of T-sg follows a Vogel-Fulcher law ln (f/ f0) = -E-a/k(B)(T-sg - T-0) with E-a = 3.2 x 10(-22) and T-0 = 7.9 K. (C) 2 000 Elsevier Science B.V. All rights reserved.