Magnetic Properties of a' Random Binary System

The quenched random system composed of A and B magnetic atoms is theoretically investigated. The exchange integrals between A‐A and B‐B atoms, JA, JB, are assumed to be positive, bnt no restriction is imposed on the exchange integral between A‐B atoms, JAB. By using effective Hamiltonians, the transition temperature and specific heat above it are calculated in the Heisen‐berg and Ising models. It is found that the transition temperature depends on the sign of JAB in the Heisenberg model, while it does not in the Ising model. The expression of the specific heat obtained is applicable to any paramagnetic phase, without restrictions on the magnitude and sign of JA, JB, and JAB.