Spin-Fluctuation Transition in the Disordered Ising Model

model of an impurity system in semiconductors consisting of spins randomly distributed in space with a hydrogen-like distance dependence of the exchange energy in the Ising Hamiltonian has been studied. The distribution function of the exchange energy and the mean square of the magnetic moment have been calculated as functions of the concentration. It has been shown that the so-called spin-fluctuation transition, which is associated with a change in the mean square of the magnetic moment, occurs in the system of spins at the concentration close to the concentration at which the metal–insulator transition occurs in semiconductors.