Origin of spin gapless semiconductor behavior in CoFeCrGa: Theory and Experiment

Abstract

Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS), which offers potentially more advantageous properties than existing ones. These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other. Here, supported by electronic-structure calculations, we report evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (prototype LiMgPdSn) structure but exhibiting chemical disorder (${\mathrm{DO}}_{3}$ structure). CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features. The saturation magnetization $({M}_{S})$ obtained at $8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ agrees with the Slater-Pauling rule and the Curie temperature $({T}_{C})$ is found to exceed $400\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Carrier concentration (up to $250\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS. The anomalous Hall coefficient is estimated to be $185\phantom{\rule{0.16em}{0ex}}\mathrm{S}/\mathrm{cm}$ at $5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Considering the SGS properties and high ${T}_{C}$, this material appears to be promising for spintronic applications.