COMPUTER EXPERIMENT ON MIXTURES OF 2 ANISOTROPIC MAGNETS WITH DIFFERENT EASY AXES

A two-dimensional Heisenberg system of classical spins, where A- and B-spins with competing anisotropic exchange interactions are distributed at random on a square lattice, has been investigated by the Monte Carlo method. The results of the computer experiments indicate the existence of an 'oblique ferromagnetic (antiferromagnetic)' phase, OF(OAF), at low temperatures for a mixture in the intermediate range of concentration. In OF, the magnetisations of A-spin and those of B-spin are tilted oblique to the easy axes of the pure substances and cross each other at a certain angle. The spin configuration in OF is investigated and the angular distribution of spin with considerable broadness was obtained. A phase diagram in the temperature-concentration plane is drawn on the basis of the estimated critical temperatures. The range of concentration corresponding to OF at 0K turns out to be much wider than the estimate by a simple application of a mean-field theory.