Giant anisotropy of Gilbert damping in epitaxial CoFe films (Conference Presentation)

Yi Li; Fanlong Zeng; Shulei Zhang; Hyeondeok Shin; Hilal Saglam; Vedat Karakas; Ozhan Ozatay; John Pearson; Olle Heinonen; Yizheng Wu; Axel Hoffmann; Wei Zhang

doi:10.1117/12.2529734

10 September 2019 Giant anisotropy of Gilbert damping in epitaxial CoFe films (Conference Presentation)

Yi Li, Fanlong Zeng, Shulei Zhang, Hyeondeok Shin, Hilal Saglam, Vedat Karakas, Ozhan Ozatay, John Pearson, Olle Heinonen, Yizheng Wu, Axel Hoffmann, Wei Zhang

Author Affiliations +

Proceedings Volume 11090, Spintronics XII; 1109024 (2019) https://doi.org/10.1117/12.2529734
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

Tailoring Gilbert damping of metallic ferromagnetic thin films is one of the central interests in spintronics applications. Here we report a giant Gilbert damping anisotropy in epitaxial Co50Fe50 (CoFe) thin film with a maximum-minimum damping ratio of 400 %, determined by broadband spin-torque as well as inductive ferromagnetic resonance (FMR). Our CoFe films are deposited via molecular beam epitaxy at room temperature. The films are then fabricated into micron-scale devices. The first sample series, with CoFe(10 nm) and CoFe(10 nm)/Pt(6 nm), are prepared for spin-torque FMR. The second sample series, with CoFe(20 nm), are prepared for vector network analyzer FMR measurements. In addition to the fourfold magnetocrystalline anisotropy, we also find a large fourfold Gilbert damping anisotropy, along with small and consistent inhomogeneous linewidth broadening. In order to exclude the two-magnon scattering influence on linewidth, we have also conducted spin-torque FMR on a CoFe/Pt sample up to 32 GHz and we don’t find any linewidth slope softening in the frequency range. We conclude that the origin of this damping anisotropy is the variation of the spin-orbit coupling (SOC) for different magnetization orientations in the cubic lattice. The large SOC anisotropy may come from the atomic short-range order in disordered Co-Fe alloy, which preserve global cubic symmetry but can have large effects on SOC. The SOC anisotropy is further corroborated from the large crystalline the anisotropic magnetoresistance in CoFe.

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Yi Li, Fanlong Zeng, Shulei Zhang, Hyeondeok Shin, Hilal Saglam, Vedat Karakas, Ozhan Ozatay, John Pearson, Olle Heinonen, Yizheng Wu, Axel Hoffmann, and Wei Zhang "Giant anisotropy of Gilbert damping in epitaxial CoFe films (Conference Presentation)", Proc. SPIE 11090, Spintronics XII, 1109024 (10 September 2019); https://doi.org/10.1117/12.2529734

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KEYWORDS

Anisotropy

System on a chip

Ferromagnetics

Thin films

Crystals

Molecular beam epitaxy

Network security

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