Magnetic domain walls as broadband spin wave and elastic magnetisation wave emitters

Abstract

We report on the direct observation of spin wave and elastic wave emission from magnetic domain walls in ferromagnetic thin films. Driven by alternating homogeneous magnetic fields the magnetic domain walls act as coherent magnetisation wave sources. Directional and low damped elastic waves below and above the ferromagnetic resonance are excited. The wave vector of the magnetoelastically induced acoustic waves is tuned by varying the excitation frequency. The occurrence of elastic wave emission is proved by a combination of micromagnetic and mechanical finite element simulations. Domain wall emitted magnetostatic surface spin waves occur at higher frequencies, which characteristics are confirmed by micromagnetic simulations. The distinct modes of magnetisation wave excitation from micromagnetic objects are a general physical phenomenon relevant for dynamic magnetisation processes in structured magnetic films. Magnetic domain walls can act as reconfigurable antennas for spin wave and elastic wave generation. The wave orientation can be controlled separately via the domain wall orientation for elastic waves and via magnetization orientation for magnetostatic surface spin waves.

Direct observation of coherent magnons with suboptical wavelengths in a single-crystalline ferrimagnetic insulator

“…It has been shown that local magnetic formations such as domain walls [45][46][47], edge bound demagnetizing fields [33,48,49], or vortices [23,24,50] can function as spin wave emitters offering effective "antenna" widths well below 200 nm. A major advantage of this approach is that the devices providing such formations are a lot larger than these effective widths.…”

Optically Inspired Nanomagnonics with Nonreciprocal Spin Waves in Synthetic Antiferromagnets

“…Recently, nanoscale spin textures in magnetic materials have gained attention for their potential as functional elements in spin‐wave devices. In particular, spin‐wave guiding, generation, and tunable transmission were observed at naturally occurring spin textures such as vortices and domain walls.…”

Magnetic texture based magnonics

“…All the experiments in the references listed here so far were based on a laser-scanning approach, where the spatial profile of magnons is acquired by moving the sample with respect to a focused laser. In a recent work Holländer and coworkers [207] could observe magnons emitted from magnetic domain walls [208] using a wide-field Kerr microscopy, as shown in Fig. 14(a) using a picosecond laser system synchronized to a CCD camera as described in detail in Ref.…”