Nanomechanics Research Group
NTT Basic Research Laboratories
3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-0198 Japan

Electromechanics  Optomechanics  Magnomechanics  Nonlinear mechanics  Phononic crystals and waveguides 

Recent Activities
On-Chip Coherent Transduction between Magnons and Acoustic Phonons in Cavity Magnomechanics
D. Hatanaka, M. Asano, H. Okamoto, Y. Kunihashi, H. Sanada, and H. Yamaguchi, Phys. Rev. Applied 17, 034024 (2022)
Coherent control of collective spin excitations (magnons) with acoustic phonons is a key technology for future hybrid spintronics devices. Surface acoustic waves (SAWs), owing to their high frequency, short wavelength, and low radiation loss, could provide an appropriate platform for integrating the devices on a chip. However, the tiny coupling efficiency in previous experiments using traveling SAWs limits the availability of this prospect. We report a planar cavity magnomechanical system, where standing acoustic waves (i.e., a SAW cavity) enhance the spatial and spectral power density to implement magnified magnon-phonon coupling. Excitation of spin-wave resonance involves significant acoustic power absorption approaching 90%, whereas the collective spin motion exerts hybridization force on the cavity dynamics, leading to coupling cooperativity exceeding unity at room temperature in such a chip-scale device. The cavity magnomechanical system paves the way to the coherent acoustic control of magnons and the development of alternative spin-acoustic technologies for classical and quantum applications.
Mode-sensitive magnetoelastic coupling in phononic-crystal magnomechanics
D. Hatanaka, and H. Yamaguchi, APL Materials 9, 071110 (2021)
The acoustically driven spin-wave resonance in a phononic-crystal cavity is numerically investigated. The designed cavity enables confinement of gigahertz vibrations in a wavelength-scale point-defect structure and sustains a variety of resonance modes. Inhomogeneous strain distributions in the modes modify the magnetostrictive coupling and the spin-wave excitation susceptible to an external-field orientation. In particular, a monopole-like mode in the cavity having a near-symmetrical pattern shows a subwavelength-scale mode volume and can provide a versatile acoustic excitation scheme independent of the field-angle variation. Thus, the phononic-crystal platform offers an alternative approach to acoustically control the spin-wave dynamics with ultrasmall and inhomogeneous mode structures, which will be a key technology to integrate and operate large-scale magnomechanical circuits.

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