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

• The ab-initio calculations predict half-metallic nature for the alloy.
• Saturation magnetization (MS) gives characteristics of half-metallic nature.
• Current spin polarization (P) value of 0.67±0.02 is deduced from PCAR measurements.
• Deduced P is higher than those obtained for many ternary and/or quaternary alloys.
• Resistivity behavior gives signature of high P at elevated temperatures.

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 (MS) of about 2 µB/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-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 (~150 K) as well. All these suggest that CoFeCrAl is a promising material for the spintronic devices.