Speaker
Description
With quantum computing on the rise, there is an increased need to deal with cryogenic environments, often involving superconducting materials. Hybrid systems utilizing spin waves at cryogenic temperatures could benefit from increased conversion efficiency of electrical and magnonic signals and feature tunable devices, changing their functionality upon crossing the critical temperature of the superconductors involved. The ferromagnet/superconductor (FM/SC) heterostructures also offer enhanced nonreciprocity of the group velocity of Damon–Eshbach spin waves unmatched by other approaches [1,2]. This could be utilized in switchable isolators or non-reciprocal couplers, which are essential components of modern microwave circuits.
Knowledge of the spin-wave dispersion relation is essential for the characterization of spin-wave behavior as well as for the explanation of many magnonic phenomena. In the past years, theoretical models of FM/SC systems have been developed [2, 3], predicting the nonreciprocal upshift in the spin-wave dispersion relation. While there were reports on the frequency upshift [4], the nonreciprocity was yet to be observed.
We will present a variable-gap propagating spin-wave spectroscopy [5] experiment of FM/SC multilayers, determining the spin-wave dispersion relation in a wide frequency and wavevector range, confirming the spin-wave nonreciprocity. The measured dispersion relations compare well to COMSOL simulations and analytical models. The experiments were performed in a 2–300 K temperature range in a commercial cryogenic setup using custom-made high-frequency (0.1–50 GHz) sample holders.
[1] M. Mruczkiewicz and M. Krawczyk, J. Appl. Phys. 115 (2014) 113909
[2] I. A. Golovchanskiy et al., J. Appl. Phys. 124 (2018) 233903
[3] X.H. Zhou et al., Phys. Rev. B 110 (2024) L020404
[4] M. Borst et al., Science 382 (2023) 430–434
[5] M. Vaňatka et al., Phys. Rev. Applied 16 (2021) 054033