On the Electronic Structure of MnB

The monoborides of Mn, Fe and Co are ferromagnetic and the saturation magnetisation indicates that the numbers of 3d electrons are 8.1, 8.9 and 9.7 respectively. A three band model described by MB 2spα* 3dβ 4sγ where 2sp implies hybridised 2s, 2p states, has been proposed for these borides. Covalent 2-sp bonding is discussed and the requirement of unsaturated covalency implies empty 2sp levels at the Fermi surface. These levels can receive scattered conduction electrons and may cause the electrical properties to differ from those of the pure transition metals. Expressions are derived relating the resistivity in the neighbourhood of the Curie temperature to the density of electronic states and the results are applied to Ni and MnB. Unfortunately the matrix elements for the scattering transitions and the 3d band form are unknown factors. It seems, however, necessary to postulate a high density of 2sp states to explain experimental data