Universality of the spin-glass transition in the Cd/sub 1-x/Mn/sub x/Te system

Universality of the spin-glass (SG) transition in bulk Cd/sub 1-x/Mn/sub x/Te was investigated by determining the scaling behavior of the spin-glass order parameter q as a function of the reduced temperature t= (T/sub g/-T)/T/sub g/, where T/sub g/ 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/chi(T)]/sup -1/. C and Θ, the Curie and Curie-Weiss parameters, were obtained from a non-linear regression of the dc low field susceptibility chi(T) above T/sub g/. q(T) thus obtained exhibits the cannonical order parameter criteria, viz. q(T>T/sub g/)=0, q(T→T/sub g/)→0, and q(T→O)→1. In range of Mn concentration studied (0.3 ≤ x ≤ 0.55), T/sub g/ ranged between 13 K and 23.5 K. Thus q as a function of absolute temperature behaves differently for different chi. However, universality is clearly evidenced when the dependence on t is determined. q(t) exhibits a universal scaling law. The authors observe q --t/sup β/ withβ ≅ 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 Cd/sub 1-x/Mn/sub x/Te system we find Θ<0, indicating a net antiferromagnetic interaction and absolute value of Θ/T/sub g/ > 1 as opposed to the SK model. They believe this to be additional evidence that the spin interactions are not distributed as a Gaussian function