Surface-specific thermal spin-depolarization on the half-metallic Heusler films

Kazuki Sumida; Masaaki Kakoki; Yuya Sakuraba; Keisuke Masuda; Kazuki Goto; Takashi Kono; Koji Miyamoto; Yoshio Miura; Kazuhiro Hono; Taichi Okuda; Akio Kimura

doi:10.1038/s42005-024-01918-w

Article Surface-specific thermal spin-depolarization on the half-metallic Heusler films

Kazuki Sumida ; Masaaki Kakoki ; Yuya Sakuraba ; Keisuke Masuda ; Kazuki Goto ; Takashi Kono ; Koji Miyamoto ; Yoshio Miura ; Kazuhiro Hono ; Taichi Okuda ; Akio Kimura

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Kazuki Sumida, Masaaki Kakoki, Yuya Sakuraba, Keisuke Masuda, Kazuki Goto, Takashi Kono, Koji Miyamoto, Yoshio Miura, Kazuhiro Hono, Taichi Okuda, Akio Kimura. Surface-specific thermal spin-depolarization on the half-metallic Heusler films. Communications Physics. 2025, 8 (), 12. https://doi.org/10.1038/s42005-024-01918-w

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Half-metallic ferromagnets exhibit a perfect spin-polarization at the Fermi energy (EF). Among
many candidates, Co2MnSi Heusler alloy is the most vigorously investigated material from both
fundamental and practical perspectives due to its half-metallic nature and high Curie temperature
(TC) of 985 K. Magnetic junction devices using Co2MnSi thin-film are known to show remarkable
performance at low temperatures. However, the performance is significantly degraded at room
temperature, which requires a detailed understanding of the temperature dependence of the electronic structure of Co2MnSi films. Here, using high-resolution spin- and angle-resolved photoelectron spectroscopy combined with first-principles slab calculations, we experimentally determined the temperature- and momentum-dependent surface spin-polarization of Co2MnSi thin-film. The recorded spin-polarization around EF at 50 K (300 K) reaches ∼75% (∼50%) at the X point, while it is ∼60% (∼30%) at the Fermi momentum. The observed surface-specific spin-depolarization behavior can be described by the thermally excited magnon model even well below TC, and we conclude that the spin fluctuation is markedly enhanced on its surface. Our findings provide important insights into the temperature-dependent electronic structure of half-metallic ferromagnet Heusler thin films, which could have significant implications for future spintronic applications.

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