High spin polarization and large spin splitting in equiatomic quaternary CoFeCrAl Heusler alloy

TL;DR

This study combines experimental and theoretical methods to demonstrate that CoFeCrAl Heusler alloy exhibits high spin polarization, large spin splitting, and half-metallic properties, making it promising for spintronic applications.

Contribution

It provides the first comprehensive investigation of CoFeCrAl alloy's electronic and magnetic properties, confirming its half-metallic nature and high spin polarization through experiments and ab-initio calculations.

Findings

Saturation magnetization of ~2 μB/f.u. at 8 K

High spin polarization of 0.67 from PCAR measurements

Predicted half-metallic electronic structure with 0.31 eV spin splitting

Abstract

In this paper, we investigate CoFeCrAl alloy by means of various experimental techniques and ab-initio calculations to look for half-metallic nature. The alloy is found to exist in the cubic Heusler structure, with presence of B2 ordering. Saturation magnetization (MS) value of about 2 Bohr magneton/f.u. is observed at 8 K under ambient pressure, which is in good agreement with the Slater-Pauling rule. MS values are found to be independent of pressure, which is a prerequisite for half-metals. The ab-initio electronic structure calculations predict half-metallic nature for the alloy with a spin slitting energy of 0.31 eV. Importantly, this system shows a high current spin polarization value of 0.67 [with error of 0.02], as deduced from the point contact Andreev reflection (PCAR) measurements. Linear dependence of electrical resistivity with temperature indicates the possibility of reasonably high spin polarization at elevated temperatures (~150 K) as well. All these suggest that CoFeCrAl is a promising material for the spintronic devices.