Phase reciprocity of spin-wave excitation by a microstrip antenna

Abstract

Using space-, time-and phase-resolved Brillouin light scattering spectroscopy we investigate the difference in phase of the two counterpropagating spin waves excited by the same microwave microstrip transducer. These studies are performed both for backward volume magnetostatic waves and magnetostatic surface waves in an in-plane magnetized yttrium iron garnet film. The experiments show that for the backward volume magnetostatic spin waves (which are reciprocal and excited symmetrically in amplitude) there is a phase difference of π associated with the excitation process and thus the phase symmetry is distorted. On the contrary, for the magnetostatic surface spin waves (which are non-reciprocal and unsymmetrical in amplitude) the phase symmetry is preserved (there is no phase difference between the two waves associated with the excitation). Theoretical analysis confirms this effect.

Generation of propagating spin waves from regions of increased dynamic demagnetising field near magnetic antidots

“…Now, the spin wave caustics on both sides of the antidot are symmetrical in both amplitude and phase. 54 This calculation directly confirms the hypothesis of negative interference put forward in Ref. 25 to explain the origin of the extinction lines.…”

“…First, there is significant asymmetric excitation of plane magnetostatic surface spin waves (which are primarily observed on the left side of the antidot), as a result of the finite width of the microstrip and the nonreciprocal character of said spin waves. 16,54 Second, in addition to the caustic beams on the right side of the antidot, there are clear "extinction" lines on the left side. Third, the angle at which the spin wave caustics are emitted depends upon the frequency of excitation.…”

Magnetization pinning at a Py/Co interface measured using broadband inductive magnetometry

“…It is known that spin waves are excited by stripline transducers resonantly, so that a microwave field of the frequency ω excites a spin wave with the same frequency (see e.g. [21,[28][29][30]) with in-plane wavenumber k determined by the spin wave dispersion ω(k). The amplitude of an excited spin wave with wavector k is proportional to the amplitude of the corresponding spatial Fourier-component of the transducer's microwave magnetic field h ek .…”

Strong asymmetry of microwave absorption by bilayer conducting ferromagnetic films in the microstrip-line based broadband ferromagnetic resonance

“…If necessary, the expressions we obtain can be easily extended to describe excitation of propagating spin waves following suggestions in Ref. [21] and Ref. [9].…”