Surface properties of Co$_2$MnAl Heusler alloy

Using the plane-wave pseudopotential method within the framework of density functional theory, Co$_2$MnAl (100), (110), and (111) surfaces with different atomic terminations have been studied in the context of some key spintronics properties, viz., surface energy, half-metallicity, magnetization, and magnetic anisotropy. The present study reveals that the MnAl-(100), Co-Al-(111), and Al-(111) surfaces exhibit negative surface energies over a wide range of chemical potentials, indicating their strong structural stability. The MnAl-(100), CoCoMnAl-(110), and Co-Mn-(111) surfaces maintain the nearly half-metallic nature like the bulk-Co$_2$MnAl, while this nearly half-metallic nature even improved for the Al-(111) surface. In contrast, the rest of the considered surfaces, CoCo-(100), Co-Al-(111) and Mn-(111) surfaces, display the strong metallic nature. Magnetization is enhanced for most surface configurations, except for Al-(111), where it decreases due to reduced moments of the exterior atoms. Regarding magnetic anisotropy, only the MnAl-(100) and Co-Mn-(111) surfaces exhibit the positive magneto-crystalline anisotropy of $\sim$0.23 and $\sim$0.33 mJ/m2, respectively. All these findings suggest that the Co-Mn-(111) and MnAl-(100) surfaces are quite appealing for spintronics applications, considering the structural stability, electronic properties, and magnetic anisotropy.