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Proceedings Paper

Giant anisotropy of Gilbert damping in epitaxial CoFe films (Conference Presentation)
Author(s): Yi Li; Fanlong Zeng; Shulei Zhang; Hyeondeok Shin; Hilal Saglam; Vedat Karakas; Ozhan Ozatay; John Pearson; Olle Heinonen; Yizheng Wu; Axel Hoffmann; Wei Zhang

Paper 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.

Paper Details

Date Published: 10 September 2019
Proc. SPIE 11090, Spintronics XII, 1109024 (10 September 2019); doi: 10.1117/12.2529734
Show Author Affiliations
Yi Li, Argonne National Lab. (United States)
Fanlong Zeng, Fudan Univ. (China)
Shulei Zhang, Argonne National Lab. (United States)
Hyeondeok Shin, Argonne National Lab. (United States)
Hilal Saglam, Argonne National Lab. (United States)
Vedat Karakas, Bogaziçi Univ. (Turkey)
Ozhan Ozatay, Bogaziçi Üniv. (Turkey)
John Pearson, Argonne National Lab. (United States)
Olle Heinonen, Argonne National Lab. (United States)
Yizheng Wu, Fudan Univ. (China)
Axel Hoffmann, Argonne National Lab. (United States)
Wei Zhang, Oakland Univ. (United States)

Published in SPIE Proceedings Vol. 11090:
Spintronics XII
Henri-Jean M. Drouhin; Jean-Eric Wegrowe; Manijeh Razeghi, Editor(s)

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