ABSTRACT
A spin-polarized current with the polarization direction perpendicular to a disk in the vortex ground state will result in renormalization of the effective damping of excitations on this state. As the current is increased to a threshold current Ic the effective damping will be zero and the lowest threshold current corresponds to the vortex gyrotropic mode. For larger values of the current the excitation is a nonlinear gyrotropic mode having nonsmall amplitudes and larger frequency than the linear mode. This effect occurs for any mode of the vortex-state disk, and the value of Ic is proportional to the mode frequency.
ABSTRACT
It is shown that stationary vortex structures can be excited in a ferrite film, in the important centimeter and millimeter wavelength ranges. It is shown that both linear and nonlinear structures can be excited using a three-beam interaction created with circular antennas. These give rise to a special phase distribution created by linear and nonlinear mixing. An interesting set of three clockwise rotating vortices joined by one counter-rotating one presents itself in the linear regime: a scenario that is only qualitatively changed by the onset of nonlinearity. It is pointed out that control of the vortex structure, through parametric coupling, based upon a microwave resonator, is possible and that there are many interesting possibilities for applications.
ABSTRACT
The magnon mode excitation spectrum is obtained from a linearized set of Landau-Lifshitz equations for vortex ground state cylindrical nanomagnets in an external magnetic field. It is shown that there is a rich spectrum of doublet states, and the splitting can be amplified in an external magnetic field.
