The structure and dynamics of magnetic vortices and solitons in multilayer ferromagnetic nanostructures.

Abstract

The structure and dynamics of magnetization in a vortex spin-transfer nanooscillator, which is a three-layer spin-valve magnetic nanopillar with a small diameter, is studied during the passage of a spin-polarized current. Using micromagnetic simulation [1,2], we studied the dynamic change in the vortices structure, the formation of the C-structure vortex state and edge vortices, the trajectory of movement and the time it takes to reach different dynamic modes. The time needed for the vortices to reach different dynamic modes was found. The possibility of the dynamic generation of radial edge vortices without the presence of a Dzyaloshinsky field or an external inhomogeneous magnetic field is shown. We demonstrate that a vortex in a thick magnetic layer can be a generator of spin waves in a thin magnetic layer with an adjustable oscillation frequency. We consider also multilayer magnetic structures, which are periodically alternating layers of two materials with different physical properties. In such systems it is possible to generate localized magnetization waves (LMW) of the magnetic solitons and breathers type [3]. Special interest in magnetic solitons and breathers is currently associated with the appearance of new experimental techniques that allow to study formation and propagation of localized magnetization waves of nanometer dimensions and their interaction with domain walls (DW). The possibility of controlling the structure and dynamic parameters of magnetic solitons and breathers using an external magnetic field is shown [4]. Dependences of the center of the DW and amplitudes of the LMW on time are constructed and analyzed in the presence of three, five and seven layers. It is shown that the LMW vibrations for the case of five layers can be described by two harmonic oscillators, for the case of seven layers, three harmonic oscillators. This work was supported by RFBR, project No19-02-00316\19 and No20-31-90048.