Elastic properties of reentrant spin glass

Abstract

Young's modulus (E) and the sound velocity (v) of the alloy series Fe_80−xNi_xCr₂₀ were measured using a vibrating reed technique for 14≤x≤30 in the temperature range 1.5-300 K. The measurement, done over a large range of x and T, made it possible to study and compare the elastic manifestation of various magnetic transitions in a single alloys series, from long-range antiferromagnet (AFM) to long-range ferromagnet (FM) through intermediate phases of spin glass (SG) and reentrant spin glass (RSG). The magnetic contribution to E and v is found to be qualitatively similar in FM and RSG alloys (both positive) and that it tends to zero as x→x_c, where x_c is the critical nickel concentration for the onset of ferromagnetism. In the spin glass (x<x_c), the magnetic contribution is negative and shows a minimum near the spin-glass transition. E has also been measured in an applied field H(=0.02 T) as a function of temperature (T<T_c) to study the contribution of magnetic domains to E in alloys with ferromagnetic and reentrant spin-glass transitions. It is found that in RSG alloys, the domain-related contribution to E vanishes below the reentrant transition.