Insight into the magnetic moment of iron borides: theoretical consideration from the local coordinative and electronic environment

Abstract

Experimentally observed magnetic properties are usually statistically averaged from bulk materials and information associated with the local chemical environment cannot be specified. Against this backdrop, we propose a theoretical strategy to provide an in-depth understanding of the multi-role for metrics that may contribute to the apparent magnetic moment of iron borides. In particular, we demonstrate this strategy through systematic manipulation of the iron/boron stoichiometry of six prototype iron borides to tune their associated local structural and electronic environment to further modulate the resultant magnetic moment. The local coordinative structures of the six iron borides were resolved utilizing bond valence analysis by taking the different coordination shells into account. Furthermore, the local electronic properties of each Fe atom in these iron borides, such as charge transfer, electronic distribution, bonding feature and orbital energy level, were carefully analyzed by Bader analysis, density of states analysis and Crystal Orbital Hamilton Population analysis. From the combination of analyses of both the coordinative and electronic properties of the prototype iron borides, a linear relationship between the local magnetic moment and the bond valence as well as the average energy of the Fe 3d orbitals has been confirmed.