The anisotropy induced by defects of "random local field" type in O(n) models and suppression of the Imry-Ma inhomogeneous state

Abstract: We demonstrate that in the system with anisotropic distribution of the defect-induced random local field directions in the n-dimensional space of vector order parameter with the O(n) symmetry, the defect-induced effective anisotropy arises for the space dimensionality 2<d<4. If the anisotropy constant exceeds the threshold value, then an inhomogeneous state predicted by Imry and Ma becomes energetically unfavorable, and the system goes back to the state with the long-range order.