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

¹ Institute of Physics, Chinese Academy of Sciences - Beijing 100190, China
² Beijing National Laboratory for Condensed Matter Physics - Beijing 100190, China

^a bgliu@mail.iphy.ac.cn

Received: 29 August 2010
Accepted: 27 January 2011

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 Tran F. and Blaha P., Phys. Rev. Lett., 102 (2009) 226401) 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 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) 0.318 eV, 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.