Competing magnetic and spin gap-less semiconducting behaviour in fully compensated ferrimagnet CrVTiAl: Theory and Experiment

TL;DR

This study combines experimental and theoretical analysis to reveal that CrVTiAl alloy exhibits a unique combination of fully compensated ferrimagnetism and spin gap-less semiconducting behavior, with multiple configurations influencing its properties.

Contribution

It provides the first comprehensive experimental and theoretical investigation of CrVTiAl's magnetic and electronic properties, highlighting its potential as a spin gap-less semiconductor with ferrimagnetic order.

Findings

CrVTiAl crystallizes in a LiMgPdSn type structure with antisite disorder.

The alloy exhibits ferrimagnetic transition near 710 K with low coercivity.

The material shows semiconducting and spin gap-less semiconducting behaviors depending on configuration.

Abstract

We report the structural, magnetic and transport properties of polycrystalline CrVTiAl alloy along with first principles calculations. It crystallizes in the LiMgPdSn type structure with lattice parameter 6.14 \AA\ 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 field of 100 Oe at 3 K. Very low moment and coercive field indicate fully compensated ferrimagnetism in the alloy. Temperature coefficient 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 configurations are studied theoretically. All the three configurations are found to be different forms of semiconductors. Ground state configuration 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 configuration is also ferrimagnetic, but has spin-gapless semiconducting nature. The highest energy configuration corresponds to a non-magnetic gapless semiconductor. The energy differences among these configurations are quite small ($<$ 1 $\mathrm{mRy/atom}$) which hints that at finite temperatures, the alloy exists in a disordered phase, which is a mixture of the three configurations. By taking into account the theoretical and the experimental findings, we conclude that CrVTiAl is a fully compensated ferrimagnet with predominantly spin gap-less semiconductor nature.