In ferromagnetic materials, waves of magnetization called spin waves can propagate, as well as the commonly known acoustic waves resulting from mechanical deformation. These two types of waves can also interact with each other. A team from the Institute of Spintronics and Quantum Information has determined the conditions under which this coupling is observed in structures where a magnetic layer is deposited on an non-magnetic substrate. The results of the studies were published in the prestigious journal: Nano Letters.
We studied the coupling between spin waves in a thin magnetic multilayer (precessing magnetization is illustrated as red cones in the figure) and surface acoustic waves (the acoustic Lowe wave is shown as a displacement of blocks). We have found that in addition to the well-known conditions, such as matching the frequencies and lengths of the two types of waves, or choosing the right wave polarization and direction of propagation relative to the magnetic field, the profile of the waves in the direction perpendicular to the surface is also important for the interaction.
The research (sample fabrication, theory and numerical simulations, and measurements) was conducted by the Poznan team, in cooperation between UAM and the Institute of Molecular Physics of the Polish Academy of Sciences in Poznan. The work was carried out under NCN grant: 2016/21/B/ST3/00452. Thanks to funding from the ID-UB program, the results were presented at the most important scientific conferences in the field of magnetism, in the form of invited lectures (Intermag 2021 - Lyon and MMM 2022 - New Orleans), and information about the publication was featured on the cover of the journal: Nano Letters.
Nandan K. P. Babu, Aleksandra Trzaskowska, Piotr Graczyk, Grzegorz Centała, Szymon Mieszczak, Hubert Glowinski, Milosz Zdunek, Slawomir Mielcarek, and Jaroslaw W. Klos, The Interaction between Surface Acoustic Waves and Spin Waves: The Role of Anisotropy and Spatial Profiles of the Modes, Nano Letters 21, 946-951 (2021), DOI:10.1021/acs.nanolett.0c03692.