Weak disorder in a two-dimensional dipole magnet

The effect of ''random-field'' disorder and ''random-anisotropy-axis'' disorder on a two-dimensional dipole ferromagnet is investigated. It is shown that disorder results in instability of the ferromagnetic phase. The correlation function of the magnetization is calculated with the aid of a self-consistent harmonic approximation. It is found that in the presence of a random field the correlation function is a power-law function of the distance. In the presence of random anisotropy the correlation function decreases logarithmically slowly as a function of distance. (C) 1997 American Institute of Physics.