Magnetic Behavior of anS=12Amorphous Antiferromagnet

Abstract

The magnetic behavior of bound shallow donors in CdS, a model $S=\frac{1}{2}$ amorphous antiferromagnet, has been measured by a Faraday rotation technique down to $T\ensuremath{\sim}50$ mK. The susceptibility, $\ensuremath{\chi}$, and $\frac{d\ensuremath{\chi}}{\mathrm{dT}}$ as well increase monotonically with decreasing $T$ with no sign of an ordering transition even though the median exchange interaction of a spin is \ensuremath{\sim}7 K. The results agree with a hydrogeniclike exchange model which is solved in terms of exactly diagonalized weakly interacting clusters.