Excitation of self-localized spin-wave bullets by spin-polarized current in in-plane magnetized magnetic nanocontacts: A micromagnetic study

Abstract

It was shown by micromagnetic simulation that a current-driven in-plane magnetized magnetic nano-contact, besides a quasi-linear propagating ("Slonczewski") spin wave mode, can also support a nonlinear self-localized spin wave "bullet" mode that exists in a much wider range of bias currents. The frequency of the "bullet" mode lies below the spectrum of linear propagating spin waves, which makes this mode evanescent and determines its spatial localization. The threshold current for the excitation of the self-localized "bullet" is substantially lower than for the linear propagating mode, but finite-amplitude initial perturbations of magnetization are necessary to generate a "bullet" in our numerical simulations, where thermal fluctuations are neglected.Consequently, in these simulations the hysteretic switching between the propagating and localized spin wave modes is found when the bias current is varied.

Spin-torque driven magnetization dynamics: Micromagnetic modeling

“…The spatial profile of this dissipation increase and the maximum dissipation value at the area border should be chosen carefully: if the profile is too steep, wave reflection can still occur due to too rapid a change of the medium properties. The rigorous theory how to choose such a profile is also not available (although numerical criteria whether the profile is chosen correctly, do exist [62,63]), so the corresponding operation is still more art than science.…”

Combined Frequency-Amplitude Nonlinear Modulation: Theory and Applications

“…(3) and (4) may be understood by assuming that AM and FM phenomena take place at the same time. From a more general viewpoint, these assumptions simply describe a non-negligible intrinsic nonlinear dependence of both amplitude and frequency on the input stimulus, as it happens in many real systems (mechanical [3]- [5], magnetoelectronic [6][7][8][9][10][11][12][13][14][15][16][17][18] and optical [19], to cite a few). However, these functional dependences might be quite complicated, so that the derivation of the corresponding Fourier spectra might be, in some cases, precluded.…”

Excitation of spin waves by a current-driven magnetic nanocontact in a perpendicularly magnetized waveguide

“…We also assume that the waveguide is magnetized to saturation by the bias magnetic field of the magnitude H e directed along the axis z. In contrast with the classical nano-contact geometry [7,12,[20][21], where the spin-wave mode excited by a nano-contact can propagate radially in the unrestricted two-dimensional "free" layer, in this case the excited spin waves can only propagate along the axis "x" of a quasi-one-dimensional waveguide. This reduction of dimensionality in the wave propagation has a profound effect on the properties of spin wave modes excited in this waveguide geometry.…”