Noncubic behavior of antiferromagnetic transition-metal monoxides with therocksalt structure

We give evidence that some nonmagnetic (i.e., spin-integrated) properties o f the antiferromagnetic Late transition-metal monoxides (MnO, FeO, CoO, NiO ) are substantially noncubic below the Neel temperature even when assuming the ideal rocksalt structure for the ions. Our findings, which are at varia nce with the currently accepted picture, are based on ab initio and model c alculations for the case study of MnO. The calculated zone-center optic pho non frequencies and Born effective charge tensor of this material show a si gnificant magnetic-induced anisotropy.