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 s ymmetry 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 roc k-salt structure to be unstable against distortions and justifies the obser ved antiferromagnetic ordering. This stress has a purely magnetic origin an d may be important in any system where the coupling between spin ordering a nd structure is strong.