Low damping Co₂₅Fe₇₅ devices for spin oscillator applications

Co₂₅Fe₇₅ films have garnered considerable attention due to their unique combination of ultralow damping, significant magnetostriction, and long spin-wave attenuation length while being metallic. These properties make them an ideal candidate for charge-based spintronic applications, including spin oscillators and hybrid phonon-magnon systems [1-2]. In this study, we synthesized CoFe films and nanostructures using DC magnetron sputtering and ebeam lithography. The resulting samples were characterized with ferromagnetic resonance (FMR), anisotropic magnetoresistance (AMR), spin torque-ferromagnetic resonance (ST-FMR), and magnetostriction measurements. We obtained low damping (α_eff ~ 4.5 x 10^-3) CoFe films and bilayers by optimizing seed layers, capping, composition, and deposition power. ST-FMR measurements of CoFe-Pt microwire devices demonstrated a significantly higher charge-to-spin conversion efficiency (~ 0.16), much larger than conventional Py-Pt devices (~ 0.05) of identical structure. These results suggest that Co₂₅Fe₇₅ is highly promising for spin oscillator and magnonic applications.

[1] A. J. Lee, J. T. Brangham, Y. Cheng, S. P. White, W. T. Ruane, B. D. Esser, D. W. McComb, P. C. Hammel, and F. Yang, Nat. Comm. 8, 234 (2017).

[2] D. Schwienbacher, M. Pernpeintner, L. Liensberger, E. R. J. Edwards, H. T. Nembach, J. M. Shaw, M. Weiler, R. Gross, and H. Huebl, Journal of Applied Physics 126, 103902 (2019).