Isotropic spin polarization in Heusler Co₂FeAl thin films

Spin polarization and the Gilbert damping, as the two key parameters of the magnetic materials for spintronic applications, were suggested to be inversely proportional to each other in a series of Heusler alloys. Recently, large anisotropic Gilbert damping was found in Co2FeAl thin films, implying that spin polarization may be also anisotropic. Here, we report an isotropic spin polarization with a constant value of 60% in a 20-nm Co2FeAl thin film with a B2 structure, using spin- and angle-resolved photoemission spectroscopy and time-resolved magneto-optical Kerr effect. Furthermore, this result was also supported by the ab initio calculations that the difference of the spin polarization between all the orientations is less than 1% for the Co2FeAl thin film. This finding provides profound insight into the spin polarization in Co2FeAl alloys. (C) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).