Magnetic properties of disordered Ising systems with various probability distributions of the exchange integrals

The disordered Ising spin-1/2 systems on square and simple cubic lattices are investigated with three types (the Handrich-Kaneyoshi's, the Gaussian, and the rectangular) of probability distribution of the exchange integrals. The general expressions of average magnetization for various distributions are derived by means of the differential operator technique. The Curie temperatures TC of the systems are calculated with the use of the effective-field theory, the correlated effective-field theory, and the improved correlated effective-field theory (ICEFT), respectively. The dependence of TC upon the parameter {Δ}, characterizing the fluctuation of the exchange integrals is given. It is obtained, under ICEFT, that for the case of the square lattice, these distributions give almost the same results and no reentrant phenomena occur, while on the simple cubic lattice, the reentrant phenomena only exist under the discrete distribution.