Origins of the significant improvement in nanocrystalline Samarium–Cobalt’s magnetic properties when doping with Niobium

Abstract

SmCo7-based compounds are prototypical rare-earth based hard magnetic materials that are the backbone of numerous devices and applications. We have found that by doping the SmCo7 phase with Niobium (e.g. SmCo6.7Nb0.3), the enhanced coercivity being measured. Using a combination of microstructural and compositional characterization techniques with ab initio calculations, we find that the Nb-doping stabilizes the nanocrystalline nature of the material by residing at the 2e site of the SmCo7 structure, decreases the average grain size, and substantially increases the magnetocrystalline anisotropy constant (K) (e.g. from 1.25×107erg/cm3 for SmCo7 to 1.40×107erg/cm3 for SmCo6.7Nb0.3). A significant enhancement in coercivity with Nb doping is attributed to the increased K and the reduced grain size.