Covalent magnetism, exchange interactions and anisotropy of the high temperature layered antiferromagnet MnB2

The investigation of the electronic structure and magnetism for the compound MnB2 with crystal structure type AlB2 has been revisited to resolve contradictions between various experimental and theoretical results present in the literature. We find that MnB2 exhibits an interesting example of a Kubler's covalent magnetism (Williams et al 1981 J. Appl. Phys. 52 2069). The covalent magnetism also appears to be the source of some disagreement between the calculated values of the magnetic moments and those given by neutron diffraction experiments. We show that this shortcoming is due to the atomic sphere approximation applied in earlier calculations. The application of the disordered local moment approach and the calculation of the inter-atomic exchange interactions within the Liechtenstein formalism reveal strong local moment antiferromagnetism with a high Neel temperature predicted from Monte Carlo simulations. A fully relativistic band structure calculation and then the application of the torque method yields a strong in-plane anisotropy of the Mn magnetic moments. The agreement of these results with neutron diffraction studies rules out any possible weak itinerant electron magnetism scenarios as proposed earlier for MnB2.