Electronic band structure calculations on thin films of the L2 ₁ full Heusler alloys X ₂YSi (X, y = Mn, Fe, and Co): Toward spintronic materials

To design half-metallic materials in thin film form for spintronic devices, the electronic structures of full Heusler alloys (Mn ₂FeSi, Fe ₂MnSi, Fe ₂FeSi, Fe ₂CoSi, and Co ₂FeSi) with an L2 ₁ structure have been investigated using density functional theory calculations with Gaussian-type functions in a periodic boundary condition. Considering the metal composition, layer thickness, and orbital symmetries, a 5-layered Co ₂FeSi thin film, whose surface consists of a Si layer, was found to have stable half-metallic nature with a band gap of ca. 0.6 eV in the minority spin state. Using the group theory, the difference between electronic structures in bulk and thin film conditions was discussed.