Substrate dependent reduction of Gilbert damping in annealed Heusler alloy thin films grown on group IV semiconductors

• Published in: Applied physics letters Vol. 119; no. 17
• Main Authors: Love, C. J., Kuerbanjiang, B., Kerrigan, A., Yamada, S., Hamaya, K., van der Laan, G., Lazarov, V. K., Cavill, S. A.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 25-10-2021
• Subjects: Annealing; Applied physics; Coercivity; Damping; Germanium; Heusler alloys; Magnetic saturation; Magnons; Silicon substrates; Thin films
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0060213

A structural and FMR study is presented for epitaxial thin films of the Heusler alloy Co2FeAl0.5Si0.5 (CFAS) grown on Ge(111) and Si(111) substrates. All films, as-grown and post-annealed, show B2 ordering; full chemical order (L21) is not obtained over the range of anneal temperatures used in this study. As-grown films show a lower Gilbert damping constant, α, when grown on a Si(111) substrate compared to Ge(111). Annealing the films to 450 °C significantly reduces α for CFAS on Ge while increasing α for CFAS on Si. This is related to a substrate dependent competition between improvements in lattice structure and increased interfacial intermixing as a function of anneal temperature. The optimal annealing temperature to minimize α is found to differ by ∼100 K between the two substrates. Above an anneal temperature of 500 °C, films grown on both substrates have increased coercivity, decreased saturation magnetization, and show characteristic two-magnon scattering features.