Magnetic stress as a driving force of structural distortions: The case of CrN

We show that the observed transition from rock salt to orthorhombic P-nma symmetry in CrN can be understood in terms of stress anisotropy. Using Local spin density functional theory, we find that the imbalance between stress stored in spin-paired and spin-unpaired Cr nearest neighbors causes the rock-salt structure to be unstable against distortions and justifies the observed antiferromagnetic ordering. This stress has a purely magnetic origin and may be important in any system where the coupling between spin ordering and structure is strong.