Predicting the spin-lattice order of frustrated systems from first principles

A novel general method of describing the spin-lattice interactions in\nmagnetic solids was proposed in terms of first principles calculations. The\nspin exchange and Dzyaloshinskii-Moriya interactions as well as their\nderivatives with respect to atomic displacements can be evaluated efficiently\non the basis of density functional calculations for four ordered spin states.\nBy taking into consideration the spin-spin interactions, the phonons, and the\ncoupling between them, we show that the ground state structure of a\nrepresentative spin-frustrated spinel, MgCr2 O4, is tetragonally distorted, in\nagreement with experiments. However, our calculations find the lowest energy\nfor the collinear spin ground state, in contrast to previously suggested\nnon-collinear models.\n