Pulsed Laser Deposition and Electron Microscopy Study of a Heterostructure Based on CoFeMnSi Heusler Alloy and Cobalt

Quaternary Heusler alloys CoFeMnSi (CFMS) are spin-gapless semiconductors. CFMS have close to 100% spin polarization of charge carriers and are promising materials for the creation of modern spintronic devices. In such devices, cobalt and its alloys are widely used to form ferromagnetic layers. The simultaneous use of these materials for the production of magnetic tunnel junctions can significantly increase the effect of tunnel magnetic resistance, which necessitates the development of a technology for the production of multilayer structures based on them. The paper considers a pulsed laser deposition method for growing a heterostructure based on a CFMS film and a cobalt layer on an MgO(100) substrate. Electron microscopic studies of cross-sectional samples showed that the resulting CFMS and cobalt layers have a perfect crystalline structure, and iron atoms were found in the cobalt layer. It was found that the thickness of the CFMS film is approximately 10 nm, the Co/Fe layer is 2 nm, and an atomically smooth boundary is formed between them. This indicates the implementation of epitaxial growth of the upper layer of the heterostructure. In the region of the interface between the MgO substrate and the CFMS film, the length of which is approximately 1 nm in the direction perpendicular to the substrate surface, depletion of CFMS atoms was detected. The presence of iron in the upper layer and the formation of an atom-depleted region at the interface between the CFMS film and the MgO substrate necessitate further optimization of the pulsed laser deposition method for the formation of heterostructures.