We study an extended Heisenberg model on the MnSi lattice. In the cubic B20 crystal structure of MnSi, Mn atoms form lattices of of corner-shared equilateral triangles. We find an ubiquitous spiral ordering along (110) for J1 <0, and J2=J3 >0, where J1, J2, and J3 are 1st, 2nd and 3rd nearest neighbor Heisenberg interactions, respectively. While the ordering direction of (110) is reasonably robust to the presence of the Dzyaloshinskii-Moriya interaction, it can be shifted to the (111) direction with the introduction of a magnetic anisotropy term for small J2/|J1|. We discuss the possible relevance of these results to the partially ordered state recently reported in MnSi.
@article{arxiv.cond-mat/0608065,
title = {A microscopic model for spiral ordering along (110) on the MnSi lattice},
author = {John M. Hopkinson and Hae-Young Kee},
journal= {arXiv preprint arXiv:cond-mat/0608065},
year = {2009}
}