Structure, magnetic property, and spin polarization of Co2FeAlxSi1−x Heusler alloys

TLDR

The study prepared off‑stoichiometric CoxFeyAl0.5Si0.5 alloys to investigate how compositional deviations affect spin polarization. Spin polarization of Co₂FeAlₓSi₁₋ₓ alloys (x = 0.0, 0.3, 0.5, 0.7) was measured by point‑contact Andreev reflection, and ab initio calculations were performed to analyze the impact of Al substitution and disorder on magnetic properties and electronic structure. Spin polarization increased from 0.57 ± 0.01 at x = 0.0 to a maximum of 0.60 ± 0.01 at x = 0.5, with off‑stoichiometric alloys exhibiting polarizations between 0.57 and 0.60 ± 0.01.

Abstract

We report the spin polarization of Co2FeAlxSi1−x (x=0.0, 0.3, 0.5, 0.7) bulk alloys measured by the point contact Andreev reflection method. All the Co2FeAlxSi1−x alloys had an L21 structure along with A2- and B2-type disorder. Several off-stoichiometric alloys (CoxFeyAl0.5Si0.5) were prepared to understand the effect of the compositional deviation from the stoichiometry on the spin polarization. By substituting Al for Si, the spin polarization changed from 0.57±0.01 for x=0.0 to a maximum value of 0.60±0.01 for x=0.5. The off-stoichiometric alloys had spin polarizations of 0.57−0.60±0.01. Ab initio calculations were performed to interpret the effect of Al addition as well as the effect of disorder on the magnetic properties and on the electronic structure.