Equilibrium magnetization of a spin glass : is mean-field theory valid ?

Abstract

Measurement of field cooled magnetization of a AgMn 10.6 % alloy as a function of temperature between 4.2 K and 50 K and magnetic field from 26 to 9 000 gauss is performed in order to link the low field and high field regimes of a spin glass. This can possibly help to define a phase diagram in the (H, T) plane as proposed by De Almeida and Thouless and Parisi and Toulouse. A closer investigation of the vicinity of Tg, above Tg, allows to compare the magnetization curves with the specific prediction of the mean-field model of Sherrington and Kirkpatrick. A qualitative good agreement is found.