Improved half-metallic ferromagnetism of transition-metal pnictides and chalcogenides calculated with a modified Becke-Johnson exchange potential
Institute of Physics, Chinese Academy of Sciences - Beijing 100190, China
2 Beijing National Laboratory for Condensed Matter Physics - Beijing 100190, China
Accepted: 27 January 2011
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 eg 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.
PACS: 75.30.-m – Intrinsic properties of magnetically ordered materials / 75.10.-b – General theory and models of magnetic ordering / 75.90.+w – Other topics in magnetic properties and materials (restricted to new topics in section 75)
© EPLA, 2011