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

In this paper, we investigate CoFeCrAl alloy by means of ab-initio electronic structure calculations and various experimental techniques. The alloy is found to exist in the B2-type cubic Heusler structure, which is very similar to Y-type (or LiMgPdSn prototype) structure with space group F-43m (#216). Saturation magnetization (M-S) of about 2 mu(B)/f.u. is observed at 8 K under ambient pressure, which is in good agreement with the Slater-Pauling rule. M-S values are found to be independent of pressure, which is a prerequisite for half-metals. The ab-initio electronic structure calculations predict half-metallicity 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 +/- 0.02, as deduced from the point contact Andreev reflection measurements. Linear dependence of electrical resistivity with temperature indicates the possibility of reasonably high spin polarization at elevated temperatures (similar to 150 K) as well. All these suggest that CoFeCrAl is a promising material for the spintronic devices. (C) 2015 Elsevier B.V. All rights reserved