Low-temperature excitations in spin glasses: evidence for a T3/2behaviour

Abstract

Presents evidence that the dominant excitations in CuMn, AgMn and AuMn spin glasses at low temperature lead to a T^3/2 behaviour in the low-temperature heat capacity and magnetisation, similar to that observed for the resistivity. This is contrary to the linear temperature dependence previously believed to describe the heat capacity of a spin glass. This evidence is obtained from a closer analysis of published specific heat and very low-temperature magnetisation measurements. The specific heat and magnetisation are correlated through a simple spin-wave model and are in accord, through the model, with independent measurements of the strength of the RKKY interaction in these alloys. The authors' own magnetisation measurements on the very dilute PdMn system also show an approximate T^3/2 behaviour at very low temperatures.