SPICE Workshop on Quantum Spinoptics, June 18th - June 20th 2024
Andrii Chumak
Faculty of Physics, University of Vienna, Austria
Yttrium-iron-garnet (YIG) is the ideal choice of material to build and develop classical and novel quantum technologies [1]. Performing propagating spin-wave spectroscopy on thin films at millikelvin temperatures is the next step toward the realization of large-scale integrated magnonic circuits for quantum applications. In the talk, I will demonstrate spin-wave propagation in a 100 nm-thick YIG film at temperatures down to 45 mK [2]. The clear transmission characteristics over the distance of 10 μm are measured from which the extracted spin-wave group velocity and the YIG saturation magnetization agree well with the theoretical values. It was also found that the magnetic moment induced in gadolinium-gallium-garnet (GGG) substrate at low temperature disturbs the magnon transport for the applied magnetic fields beyond 75 mT. To address this phenomenon, the magnetization of the GGG substrate was measured via vibrating-sample magnetometry, and the magnetic properties of the YIG film were characterized by ferromagnetic resonance (FMR) measurements [3]. The FMR studies show that at temperatures below 50 K and external applied field the paramagnetic GGG is sufficiently magnetized and induces a stray field in the YIG layer that opposes the externally applied field. The lower the temperature and the higher the external fields, the larger is the stray field. The analytical theory is developed to calculate the GGG-induced field and the comparison of the theory with experiments allows to quantify the uniaxial magnetic anistotropy, which increases with the decrease of temperature more than three times. Moreover, the magnetization of GGG increases the magnetic damping of YIG by more than eight times compared to measurements at room temperature.
- V. Chumak, P. Kabos, M. Wu, et al., “Advances in Magnetics Roadmap on Spin-Wave Computing”, IEEE Trans. Magn. 58, 1–72 (2022).
- Knauer, K. Davídková, D. Schmoll, R. O. Serha, A. Voronov, Q. Wang, R. Verba, O. V. Dobrovolskiy, M. Lindner, T. Reimann, C. Dubs, M. Urbánek, and A. V. Chumak, “Propagating spin-wave spectroscopy in nanometer-thick YIG films at millikelvin temperatures”, J. Appl. Phys. 133, 143905 (2023).
- O. Serha, A. A. Voronov, D. Schmoll, R. Verba, K. O. Levchenko, S. Koraltan, K. Davídková, B. Budinska, Q. Wang, O. V. Dobrovolskiy, M. Urbánek, M. Lindner, T. Reimann, C. Dubs, C. Gonzalez-Ballestero, C. Abert, D. Suess, D. A. Bozhko, S. Knauer, A. V. Chumak, “Magnetic anisotropy and GGG substrate stray field in YIG films down to millikelvin temperatures”, arXiv:2402.12112 (2024).