Competing Magnetic and Spin-Gapless Semiconducting Behavior in Fully Compensated Ferrimagnetic CrVTiAl: Theory and Experiment

Abstract

We report the structural, magnetic and transport properties of polycrystalline CrVTiAl alloy along with rst principles calculations. It crystallizes in the LiMgPdSn type structure with lattice parameter 6.14 A at room temperature. Absence of (111) peak along with the presence of a weak (200) peak indicates the antisite disorder of Al with Cr and V atoms. The magnetization measurements reveal a ferrimagnetic transition near 710 K and a coercive eld of 100 Oe at 3 K. Very low moment and coercive eld indicate fully compensated ferrimagnetism in the alloy. Temperature coe cient of resistivity is found to be negative, indicating a characteristic of semiconducting nature. Absence of exponential dependence of resistivity on temperature indicates a gapless/spin-gapless semiconducting behaviour. Electronic and magnetic properties of CrVTiAl for three possible crystallograpic con gurations are studied theoretically. All the three con gurations are found to be di erent forms of semiconductors. Ground state con guration is a fully compensated ferrimagnet with band gaps 0.58 eV and 0.30 eV for up and down spin bands respectively. The next higher energy con guration is also ferrimagnetic, but has spin-gapless semiconducting nature. The highest energy con guration corresponds to a non-magnetic gapless semiconductor. The energy di erences among these con gurations are quite small (< 1 mRy=atom) which hints that at nite temperatures, the alloy exists in a disordered phase, which is a mixture of the three con gurations. By taking into account the theoretical and the experimental ndings, we conclude that CrVTiAl is a fully compensated ferrimagnet with predominantly spin-gapless semiconductor nature.