Performing propagating spin-wave spectroscopy of thin films at millikelvin temperatures is the next step towards the realisation of large-scale integrated magnonic circuits for quantum applications. Here we demonstrate spin-wave propagation in a 100nm-thick yttrium-iron-garnet film at the temperatures down to 45mK, using stripline nanoantennas deposited on YIG surface for the electrical excitation and detection. The clear transmission characteristics over the distance of 10μm are measured and the subtracted spin-wave group velocity and the YIG saturation magnetisation agree well with the theoretical values. We show that the gadolinium-gallium-garnet substrate influences the spin-wave propagation characteristics only for the applied magnetic fields beyond 75mT, originating from a GGG magnetisation up to 47kA/m at 45mK. Our results show that the developed fabrication and measurement methodologies enable the realisation of integrated magnonic quantum nanotechnologies at millikelvin temperatures.
@article{arxiv.2212.02257,
title = {Propagating spin-wave spectroscopy in nanometer-thick YIG films at millikelvin temperatures},
author = {Sebastian Knauer and Kristýna Davídková and David Schmoll and Rostyslav O. Serha and Andrey Voronov and Qi Wang and Roman Verba and Oleksandr V. Dobrovolskiy and Morris Lindner and Timmy Reimann and Carsten Dubs and Michal Urbánek and Andrii V. Chumak},
journal= {arXiv preprint arXiv:2212.02257},
year = {2025}
}