A cluster model for amorphous antiferromagnetism

A simple method is outlined for the calculation of the paramagnetic spin susceptibility and the magnetic dependence of the specific heat appropriate to a random distribution of antiferromagnetically coupled spins. This method considers the microscopic sample to be a collection of clusters of various sizes. Interactions between the clusters are assumed to be weak and are included in a mean-field type of approximation. The model is specifically applied to n-type silicon (Si : P) with donor concentrations less than ∼1 × 1018 cm−3.