Superparamagnetic-like behaviour of magnetic alloys

The effect of antiferromagnetic interaction on a binary Ising ferromagnetic alloy A_pB_1?p is studied based on cluster-variational method and assuming either J_AB or J_BB or both exchange interactions to be of antiferromagnetic type. In a ferromagnetic state the moment saturates to a value much lower than its full value. Within the temperature interval where moment saturates, the system exhibits superparamagnetic-like behaviour. The induced moment becomes a function of $\text{h}\text{T}$ only, and the zero-field susceptibility follows Curie law. The incomplete saturation of moment persists up to a large value of $\text{h}\text{T}$. The short-range order parameter at T = 0 is much less than that of homogeneous ferromagnet.