Magnetization steps in Sn1-xEuxTe: Eu-Eu exchange and Eu distribution

The magnetization of Sn1-xEuxTe, with x = 0.011 and 0.042, was measured at 20 mK in magnetic fields up to 90 kOe. Magnetization steps (MSTs) from pair s and triplets were observed. The MSTs give J/k(B) = -0.311 +/- 0.006 K for the dominant Eu-Eu exchange constant. Comparisons of the magnetization cur ves with numerical simulations indicate that, instead of being distributed randomly, the Eu ions tend to bunch together. A phenomenological approach w hich uses the concept of a local Eu concentration x(L) is quire successful in describing the data for these two samples.