Controlled nonlinear magnetic damping in spin-Hall nano-devices

One of the fundamental dynamical phenomena in magnetic systems is the nonlinear damping enhancement, which imposes strict limitations on the operation and efficiency of magnetic nanodevices. For instance, nonlinear damping prevents coherent magnetization auto-oscillations driven by the spin injection into spatially extended magnetic regions [1].
We utilize micro-focus Brillouin light spectroscopy (BLS) to demonstrate that nonlinear damping can be controlled by the ellipticity of magnetization precession. By balancing the demagnetizing field with the magnetic anisotropy in a Pt/Co/Ni heterostructure, we minimize ellipticity and achieve coherent magnetization oscillations in a microscopic CoNi disk, driven by spatially extended injection of spin current generated in Pt by the spin Hall effect. Micromagnetic simulations show that the mechanism responsible for the nonlinear damping is non-resonant parametric pumping enabled by the precession ellipticity. Our results provide a novel route for the implementation of efficient active spintronic and magnonic devices driven by spin current.

[1] V. E. Demidov, S. Urazhdin, B. Divinskiy, V. D. Bessonov, A. B. Rinkevich, V. V. Ustinov and S. O. Demokritov, Nature Comm. 8, 1579 (2017)