Local field effects in half-metals: AGWstudy of zincblende CrAs, MnAs, and MnC

Abstract

We used the $\mathit{GW}$ approximation to examine the improvements of the semiconducting gap in three predicted half-metals with the zincblende structure, CrAs, MnAs and MnC, compared to density-functional theory with the generalized gradient approximation. Recognizing the differences in the local field effect between transition metals and insulators, respectively, we modeled one spin channel in a half-metal as metallic having a $d$ character and the oppositely oriented spin channel as insulating. To demonstrate the necessity of treating these three compounds as having a $d$ character, we also applied the $\mathit{GW}$ approximation to CrAs using the nearly free electron model in the conducting channel. We found that CrAs shows the least improvement, while Mn-based half-metals exhibit comparable improvements. Physical explanations for these results are presented.