Low-dc-field susceptibility ofCuMnspin glass

Abstract

Low-dc-field magnetic-susceptibility measurements are reported for $\mathrm{Cu}\mathrm{Mn}$ alloys containing 1.08- and 2.02-at.% Mn using a superconducting quantum-interference device. The zero-field cooled initial susceptibility shows a cusplike peak at $T_g$, the transition temperature to a spin-glass state. After field cooling from $T>\mathrm{}{T}_g$ (even for $H=2\mathrm{}$ G), the susceptibility below $T_g$ is nearly independent of temperature with the constant value of $\sim 0.97\chi \left(T_g\right)$. The high-temperature susceptibility follows a Curie-Weiss law until just above $T_g$; the value of the Curie temperature is very small. Using the theory of Sherrington and Kirkpatrick, the spin-glass order parameter $q\left(T\right)\mathrm{}$ is extracted from the susceptibility data. A critical index $\beta \simeq 1$ is obtained assuming a power law for $q\left(T\right)\mathrm{}\propto {(1-\frac{T}{T_g})}^{\beta }$. The results are qualitatively in agreement with the prediction of an Edwards-Anderson-type mean-field theory.