Two-dimensional microwave nonlinear spin-wave pulses in in-plane confided magnetic films

The authors demonstrate that nonlinear two-dimensional "quasi-bullets" can be formed in a confined geometry. By using the space and time-resolved Brillouin light scattering technique the formation is observe in a stripe having width w=2.5 mm cut from an YIG film of thickness L=4.9 micron. Theoretically, the effective dipole pinning of dynamic magnetization of guided backward volume magnetostatic spin wave (BVMSW) modes at the stripes lateral edges and its influence on the transverse and longitudinal attractive nonlinearity of BVMSW. It is found that the edge spins are highly pinned, and the pinning parameter for propagating BVMSW is at least not less than that of the magnetostatic surface wave standing-wave resonances across the film width. As a result the initial waveform launched into the film stripe by the input antenna has an inhomogeneous profile in the direction of the stripe width close to the shape of the lowest BVMSW width mode. The transverse instability then takes form of the nonlinear four-wave mixing of the discrete stripe wave modes. It is shown that this process is threshold-free.