Magnetic Vortex as a Spin Wave Filter

Magnonics aims to use spin-waves for data transmission and processing. However, the use of an external field jeopardizes the energy efficiency. The use of domain walls as waveguides has been proposed¹, as they exist in remanent states. Also, the waves are channeled within the wall width, due a magnetostatic potential well.
In the Landau state, the Néel wall is divided into two regions of opposite magnetization, separated by a vortex. In this work, we show, through micromagnetic simulations, that excitations performed at one region are mostly reflected by the vortex, but they can be transmitted at specific frequencies.
The frequency of the maximum transmitted wave (FTW) can be tuned by changing the uniaxial or shape anisotropy of the system. Considering a (4x1) μm² permalloy rectangle, the FTW has a quadratic behavior with the uniaxial anisotropy energy of the system, passing through a minimum of 500 MHz at 100 kJ/m³.
By fixing the aspect ratio of the rectangle, if the area is increased, the FTW decreases exponentially. E.g., for a fixed 4 μm length, the FTW can be tuned between 800 MHz and 2 GHz by varying the width.
Therefore, the vortex acts a tunable frequency filter for the channeled spin-waves.

1 - Garcia-Sanchez, et al. (2015) Narrow Magnonic Waveguides Based on Domain Walls