Improved half-metallic ferromagnetism of transition-metal pnictides and chalcogenides calculated with a modified Becke-Johnson exchange potential

TL;DR

This study demonstrates that a modified Becke-Johnson exchange potential significantly improves the prediction of half-metallic ferromagnetism in transition-metal pnictides and chalcogenides, aligning theoretical results with experimental observations.

Contribution

The paper introduces the use of a modified Becke-Johnson exchange potential in DFT calculations to accurately predict half-metallic ferromagnetism in transition-metal compounds.

Findings

mBJLDA lowers minority-spin p-bands by 0.25-0.35 eV

mBJLDA raises minority-spin e_g bands by 0.33-0.73 eV

Enhanced HM gap in several compounds by 19-56%

Abstract

We use a density-functional-theory (DFT) approach with a modified Becke-Johnson exchange plus local density approximation (LDA) correlation potential (mBJLDA) [semi-local, orbital-independent, producing accurate semiconductor gaps. see F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)] to investigate the electronic structures of zincblende transition-metal (TM) pnictides and chalcogenides akin to semiconductors. Our results show that this potential does not yield visible changes in wide TM d-t_{2g} bands near the Fermi level, but makes the occupied minority-spin p-bands lower by 0.25~0.35 eV and the empty (or nearly empty) minority-spin e_g bands across the Fermi level higher by 0.33~0.73 eV. Consequently, mBJLDA, having no atom-dependent parameters, makes zincblende MnAs become a truly half-metallic (HM) ferromagnet with a HM gap (the key parameter) 0.318eV, being consistent with experiment. For zincblende MnSb, CrAs, CrSb, CrSe, or CrTe, the HM gap is enhanced by 19~56% compared to LDA and generalized gradient approximation results. The improved HM ferromagnetism can be understood in terms of the mBJLDA-enhanced spin exchange splitting.