Fresnel diffraction of spin waves

TL;DR

This paper investigates how spin waves in a thin YIG film diffract and propagate when excited by a constricted antenna, revealing Fresnel diffraction effects through experimental mapping.

Contribution

It demonstrates the application of near-field Fresnel diffraction theory to explain spin wave focusing and oscillations observed in magnetostatic wave propagation experiments.

Findings

Spin wave beams remain focused with widths similar to the antenna constriction.

Amplitude oscillations occur within the constriction area.

Fresnel diffraction theory explains the observed propagation features.

Abstract

The propagation of magnetostatic forward volume waves excited by a constricted coplanar waveguide is studied via inductive spectroscopy techniques. A series of devices consisting of pairs of sub-micrometer size antennae is used to perform a discrete mapping of the spin wave amplitude in the plane of a 30-nm thin YIG film. We found that the spin wave propagation remains well focused in a beam shape of width comparable to the constriction length and that the amplitude within the constriction displays oscillations, two features which are explained in terms of near-field Fresnel diffraction theory.