Microwave excitation of spin wave beams in thin ferromagnetic films

TL;DR

This paper introduces a method to generate narrow, directed spin wave beams in thin ferromagnetic films using a specially designed coplanar waveguide, enabling precise control without material inhomogeneity.

Contribution

The paper presents a novel microwave excitation technique for creating localized spin wave beams in homogeneous ferromagnetic films, avoiding the need for material inhomogeneity or nonuniform bias fields.

Findings

Spin wave beams can propagate over several micrometers.

The method allows for multiple beams of different widths at the same frequency.

The approach is applicable without altering the film's homogeneity.

Abstract

We present an approach enabling generation of narrow spin wave beams in thin homogeneous ferromagnetic films. The main idea is to match the wave vector of the spin wave with that corresponding to the spectral maximum of the exciting microwave magnetic field only locally, in the region of space from which the beam should be launched. We show that this can be achieved with the aid of a properly designed coplanar waveguide transducer generating a nonuniform microwave magnetic field. The resulting two-dimensional spin wave beams obtained in micromagnetic simulations propagate over distances of several micrometers. The proposed approach requires neither inhomogeneity of the ferromagnetic film nor nonuniformity of the biasing magnetic field, and it can be generalized to yield multiple spin wave beams of different width at the same frequency. Other possible excitation scenarios and applications of spin wave beam magnonics are also discussed.