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We have investigated the interfacial structure and its correlation with the calculated spin polarization in Co2MnSi/GaAs(001) lateral spin valves. Co2MnSi (CMS) films were grown on As-terminated c(4×4) GaAs(100) by molecular beam epitaxy using different first atomic layers: MnSi, Co, and Mn. Atomically resolved Z-contrast scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) were used to develop atomic structural models of the CMS/GaAs interfaces that were used as inputs for first-principles calculations to understand the magnetic and electronic properties of the interface. First-principles structures were relaxed and then validated by comparing experimental and simulated high-resolution STEM images. STEM-EELS results show that all three films have similar six atomic layer thick, Mn- and As-rich multilayer interfaces. However, the Co-initiated interface contains a Mn2As-like layer, which is antiferromagnetic, and which is not present in the other two interfaces. Density functional theory calculations show a higher degree of interface spin polarization in the Mn- and MnSi-initiated cases, compared to the Co-initiated case, although none of the interfaces are half-metallic. The loss of half-metallicity is attributed, at least in part, to the segregation of Mn at the interface, which leads to the formation of interface states. The implications for the performance of lateral spin valves based on these interfaces are discussed briefly.
Bibliographical noteFunding Information:
This work was supported in part by C-SPIN, one of the six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA. Electron microscopy used facilities supported by the UW-Madison Materials Research Science and Engineering Center (DMR-1121288). STEM-EELS was performed in the Characterization Facility of the University of Minnesota, which receives partial support from the NSF through the MRSEC. Ab initio DFT calculations were made possible in part by a grant of high performance computing resources and technical support from the Alabama Supercomputer Authority.
© 2018 American Physical Society.