Unidirectional emission and reconfigurability of channeled spin waves from a vortex core in a teardrop-shaped nanopatch

Abstract

We propose the design of a teardrop-shaped magnetic patch as a unidirectional magnetically driven spin wave emitter capable of operating in a wide range of frequencies. We explore its potential through micromagnetic studies in line with vibrational sample magnetometry measurements and ferromagnetic resonance experiments. The proposed system is based on the excitation of a vortex core, acting as a source of spin waves, and a single Bloch domain wall, as a channel for the confinement and propagation of the mode in a sufficiently thick magnetic patch in the single magnetic vortex (SMV) state. The novelty consists in the reconfigurability and simplicity of the system, that is operational without the need of external saturating fields, retaining a single Bloch domain wall and a movable single vortex core. This allows significant suppression of the wave emission by means of an external bias field, which in turn allows a controllable valvelike effect. Following our proposed strategy for cultivating a single vortex core in the shape, and after a thorough micromagnetic study of the most prominent magnetization dynamics in the patch, we show that the SMV state can be obtained in a thick enough (80 nm) teardrop-shaped patch. Micromagnetic results show the potential of this simple structure as a tunable and unidirectional spin wave emitter. Experimental results also suggest that the required magnetic configuration has been experimentally obtained in the structure, in good agreement with micromagnetic simulations.