Universality of the Spin-Glass Transition in the Cd1−xMnXTe System

Abstract

AbstractUniversality of the spin-glass (SG) transition in bulk Cd1−xMnxTe was investigated by determining the scaling behavior of the spin-glass order parameter q as a function of the reduced temperature t = (Tg-T)/Tg, where Tg is the transition temperature. q(T) was determined from the SQUID magnetometric data both above and below the transition. It can be shown that, q(T) = 1 + T[│θ│ − C/χ(T)]−1. C and θ, the Curie and Curie-Weiss parameters, were obtained from a non-linear regression of the dc low field susceptibility χ(T) above Tg. q(T) thus obtained exhibits the cannonical order parameter criteria, viz. q(T>Tg) = 0, q(T→Tg)= 0, and q(T→Tg)→0, and q(T→0)→1. In range of Mn concentration studied (0.3 ≦ x ≦ 0.55), Tg ranged between 13 K and 23.5 K. Thus q as a function of absolute temperature behaves differently for different x. However, universality is clearly evidenced when the dependence on t is determined. q(t) exhibits a universal scaling law. We observe q ˜ tβ with β ≅ 0.95. Overall good agreement was noted with the Sherrington-Kirkpatrick (SK) infinite range SG model. Observed value of β is in excellent agreement with the model prediction β −1. But in the Cd1−xMnxTe system we find θ<0, indicating a net antiferromagnetic interaction and │θ│/Tg > 1 as opposed to the SK model. We believe this to be additional evidence that the spin interactions are not distributed as a Gaussian function.