Substitutional and interstitial doping in LaCo5 system for the development of hard magnetic properties: A first principles study

Abstract

Abstract We investigate here the changes in the electronic structure at the transition metal sites of the RE-TM5 structure (RE = Rare Earth, TM = Transition Metal) while doping the interstitial sites with nitrogen. LaCo5 compound is taken as the baseline compound owing to its critically needed intrinsic magnetic properties such as magneto-crystalline anisotropy energy (MAE) of ≈5 meV/fu [1] due to the contributions from the cobalt network. In addition, because of the lack of 4f electrons in lanthanum, complications originating from the treatment of the 4f localized electrons are absent in this compound; making it an ideal reference material to all the isostructural RE-TM5 compounds. Addition of nitrogen is shown to reduce the local spin moments of the nearest TM due to the hybridization present between N-2p states and the TM-3d states. More importantly, we showed here how a planar anisotropy becomes a strong uniaxial anisotropy after the addition of nitrogen into LaCo2Fe3 and LaCo2Mn3, and linked this transformation to the band structure changes after nitrogenation. Effect of nitrogen in Sm2Fe17 and NdFe12 is already known, in that, it increases the Curie temperature, and induces a strong magnetic anisotropy for both compounds. In this study we show that similar trends can be observed in RM-TM5 type compounds providing a challenge for experimentalists to realize these compositions through appropriate synthesis. Future studies will be conducted to understand whether the additions of nitrogen may induce a structural transformation from 1–5 into 2-12 or 2-17 type intermetallics.