Surface spin polarization of the non-stoichiometric Heusler compound Co2Mn(alpha)Si

TL;DR

This study investigates how bulk defects and surface states affect the spin polarization of Co2Mn(alpha)Si thin films, revealing that Mn content influences the sign and magnitude of spin polarization at the Fermi level.

Contribution

It combines experimental spin-resolved photoemission spectroscopy with theoretical calculations to elucidate defect and surface state effects on spin polarization in non-stoichiometric Heusler compounds.

Findings

Mn-poor alloys exhibit negative spin polarization at EF due to antisite and surface states.

Mn-rich alloys show positive spin polarization with reduced surface state influence.

Bulk defect composition critically determines the surface spin polarization behavior.

Abstract

Using a combined approach of spin-resolved photoemission spectroscopy, band structure and photoemission calculations we investigate the influence of bulk defects and surface states on the spin polarization of Co2Mn(alpha)Si thin films with bulk L21 order. We find that for Mn-poor alloys the spin polarization at EF is negative due to the presence of Co_Mn antisite and minority surface state contributions. In Mn-rich alloys, the suppression of Co(Mn) antisites leads to a positive spin polarization at the Fermi energy, and the influence of minority surface states on the photoelectron spin polarization is reduced.