Electronic structures of various (001) and (111) surfaces, interfaces and spin transport properties of half-metallic fully compensated ferrimagnet Cr2Se

Abstract

Half-metallic fully compensated ferrimagnets have advantages of extremely low net magnetic moments and large spin polarization. By employing the first-principles calculations within density functional theory combined with the nonequilibrium Green’s function, we investigated the electronic structures of Cr2Se (001), (111) surfaces and Cr2Se/CdS interface, as well as the transport properties of Cr2Se/CdS/Cr2Se magnetic tunnel junction (MTJ). Our calculations show that bulk half-Heusler alloy Cr2Se is a half-metallic fully compensated ferrimagnet with a direct spin-down bandgap. Although the half-metallic character of bulk is destroyed in all surface terminations owing to the emergence of surface states, CrBSe-(001) termination holds the lowest surface free energy and possesses the highest surface spin polarization (SP) of 83.6%. Calculations on electronic structures of Cr2Se/CdS heterostructures show that CrBSe-S-top type interface structure holds the lowest interface free energy and high interface SP of 71.6%. Moreover, the spin transport properties of Cr2Se/CdS/Cr2Se MTJ device are studied and the calculated tunnel magnetoresistance (TMR) ratio reaches up to a high value of 4.98×103, which shows that the device has great application potential in spintronic devices.