Seminarium ISQI - Dr. Matthias Küß

Title: Nonreciprocal magneto-acoustic waves in piezoelectric/ferromagnetic hybrids

Abstract:
Surface acoustic waves (SAWs) play a key role in modern technology, from telecommunications to sensing and lab-on-a-chip systems. In magnetism, magnetoelastic coupling with magnetic media in piezoelectric/magnetic hybrids enables magnetic domain manipulation, spin wave (SW) amplification, and the realization of novel microwave devices. While SAWs are inherently reciprocal, magneto-acoustic interactions can induce nonreciprocity, where transmission changes under the reversal of the propagation direction. In this talk, I will introduce the resonant coupling between SAWs and SWs, modeled by magneto-acoustic driving fields and focus on the resulting nonreciprocal effects. The symmetry of the SAW-SW coupling depends crucially on the specific mode of the SAW [1,2]. Large nonreciprocal transmission of SAWs is demonstrated in magnetic systems with a nonreciprocal dispersion relation f(+k) ≠ f(-k), such as ferromagnetic/heavy-metal bilayers with the interfacial Dzyaloshinskii-Moriya interaction [3] and synthetic antiferromagnets composed of two ferromagnetic layers separated by a thin nonmagnetic spacer layer. Because of the high tunability of the SW dispersion of synthetic antiferromagnets, the nonreciprocal transmission of SAWs can be optimized to reach very high values (>100 dB) and engineered to exhibit a wide-band-like behavior [4,5].

[1] N. K. P. Babu, A. Trzaskowska, P. Graczyk, G.Centała, S. Mieszczak, H. Głowiński, M. Zdunek, S. Mielcarek, J. W. Kłos, Nano Lett. 21, 946 (2020)

[2] M. Küß et al., Phys. Rev. Applied 15, 034046 (2021)

[3] M. Küß, M. Heigl, L. Flacke, A. Hörner, M. Weiler, M. Albrecht, and A. Wixforth, Phys. Rev. Lett. 125, 217203 (2020).

[4] R. Verba, V. Tiberkevich, and A. Slavin, Phys. Rev. Applied 12, 054061 (2019).

[5] M. Küß, S. Glamsch, A. Hörner, and M. Albrecht, ACS Appl. Electron. Mater. 6, 1790 (2024).