  Despite a plethora of materials suggested for spintronic applications, a new
class of materials has emerged, namely spin gapless semiconductors (SGS), that
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 the first-principles,
electronic-structure calculations, we report the first experimental evidence of
SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (L21)
structure but exhibiting chemical disorder (DO3 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 (MS) obtained at 8 K agrees with the Slater-Pauling rule and the
Curie temperature (TC) is found to exceed 400 K. Carrier concentration (up to
250 K) and electrical conductivity are observed to be nearly temperature
independent, prerequisites for SGS. The anomalous Hall coefficient is estimated
to be 185 S/cm at 5 K. Considering the SGS properties and high TC, this
material appears to be promising for spintronic applications.
