Magnetic Properties of the Random Mixture of Ising Spins

Abstract

A method of obtaining the magnetic properties of the random mixture of plural kinds of magnetic atoms (including nonmagnetic atoms) in both the site and the bond problems is presented. The specific heats and the susceptibilities of the one-dimensional binary mixture and the binary Bethe lattice are exactly given. The phase transitions of both the Bethe lattice and the ordinary two- and three-dimensional lattices are also discussed. It is shown that the phase boundary of an ordinary binary mixture in the site problem is rather similar to that in the bond problem when JAAJBB > 0 and JαJβ > 0, while they are quite different when JAAJBB < 0 and JαJβ < 0. In the latter case, the two critical lines of ordinary lattice, on which the uniform or the staggered susceptibility diverges, cross at some value of concentration of magnetic atoms, while they are separated by the paramagnetic phase in the bond problem. The experimental result for (MnxCr1−x)Sb is similar to the former and that for Co(SxSe1−x)2 is similar to the latter.