The paramagnetic properties of the monoborides of V, Cr, Mn, Fe, Co and Ni

Abstract

Abstract Paramagnetic measurements have been made on powder samples of VB, CrB, MnB, FeB, CoB and NiB either over the temperature range 150°K to 800°K or, in the case of those that are ferromagnetic, from the Curie point to 800°K. The data for the ferromagnetic borides are intended to supplement results obtained below the Curie point and described in an earlier paper. VB and CrB are strongly paramagnetic in the manner of transition metals but NiB is only very weakly paramagnetic and is considered to contain no holes in the 3d band. The magnetic properties together with the occurrence of the boron atoms in linear chains lead us to describe these borides in terms of a three-band model involving a broad shallow conduction band, a narrow dense 3d band and a bonding band capable of containing two electrons per boride unit; the latter band is assumed to arise from 2s2p orbitals required for covalent bonds between adjacent boron atoms. With the exceptions of CoB and VB measurements of the absolute thermoelectric power have been made between room temperature and 300°K; together with the magnetic data these results show that the properties of a boride of composition Mz B, where z is the atomic number of the metal may be correlated with those of the pure metal of atomic number z + 1.