Critical behaviour of the CdCr2×0.85In2×0.15S4insulating spin glass

Abstract

The authors have measured the field-cooled susceptibility of the CdCr2*0.85In2*0.15S4 insulating spin glass from 0.7Tg to 2Tg and for applied fields of 5 to 110 Oe. A strong temperature dependence of the non-linear susceptibility chi nl is observed when approaching Tg=16.8+or-0.1 K. This value is defined as the temperature of the maximum of the very low-field magnetisation and coincides with the onset of irreversibilities. The fit of the chi nl data to a scaling function yields delta =4.1*0.4 and phi =3.1+or-0.5 (corresponding to beta =0.75+or-0.10 and gamma =2.3+or-0.4). From the known anisotropy, Ising exponents are expected but only the gamma -value is consistent with that suggested for the critical Ising behaviour. The values of Tg and phi agree with those obtained from a previous AC measurement, supporting the picture of a phase transition at Tg from both static and dynamic points of view.