Strain Fields and the Electronic Structure of Antiferromagnetic CrN

We present a theoretical analysis of the role that strain plays on the electronic structure of chromium nitride crystals. We use LSDA+U calculations to study the elastic constants, deforma- tion potentials and strain dependence of electron and hole masses near the fundamental gap. We consider the lowest energy antiferromagnetic models believed to describe CrN at low temperatures, and apply strain along different directions. We find relatively large deformation potentials for all models, and find increasing gaps for tensile strain along most directions. Most interestingly, we find that compressive strains should be able to close the relatively small indirect gap (' 100 meV) at moderate amplitudes ' 1.3%. We also find large and anisotropic changes in the effective masses with strain, with principal axes closely related to the magnetic ordering of neighboring layers in the antiferromagnet. It would be interesting to consider the role that these effects may have on typical film growth on different substrates, and the possibility of monitoring optical and transport properties of thin films as strain is applied.