Significant Enhancement of Spin Polarization and Magnetism in the Surface State of Full‐Heusler Structural Cr₂CoGa

Abstract

For pristine full‐Heusler structural L21‐Cr2CoGa thin films, full‐potential ab initio density‐functional theory (DFT) simulations within the generalized gradient approximation (GGA) are used to investigate the structural stability, the electronic and magnetic properties of the two possible (001) surfaces. It is found that: 1) the spin polarization at the CoGa‐terminated (001) surface state decreases to 27% from 69% in bulk due to the screening of the p‐electrons of the nonmagnetic sp atom Ga at surface; 2) the spin polarization at the Cr1Cr2‐terminated (001) surface state is remarkably increased to 92% owing to the much lower density of states of minority‐spin surface states at the Fermi level. Cr1 (Cr2) atomic magnetic moments at the Cr1Cr2‐terminated (001) surface are greatly increased compared to bulk. Furthermore, it is unveiled that the Cr1Cr2‐terminated (001) surface is more stable than the CoGa‐terminated (001) for the lower surface energy over the whole effective chemical potential. This surprising report indicates that the full‐Heusler structural L21‐type Cr2CoGa thin films are promising candidates for the next‐generation spintronic materials.