講演情報
[23a-A201-11]Observation of parametric oscillation bi-stability in magnetic disk
〇(D)Kosuke Umemura1, Tomosato Hioki1,4, Eiji Saitoh1,2,3,4,5 (1.Dept. Appl. Phys., Univ. of Tokyo, 2.BAI Univ. of Tokyo, 3.QPEC, Univ. of Tokyo, 4.Tohoku Univ., 5.JAEA)
キーワード：
spintronics、spin-wave、magnetization dynamics
Spin waves are magnetization dynamics in which the precession of magnetization propagates as a wave. Spin waves have strong nonlinearities due to dipole and exchange interactions, and there are abundant nonlinear processes between spin waves with different wavenumbers. An example of a linear excitation process is ferromagnetic resonance (FMR), which can excite a uniform precession of magnetization, i.e., a spin-wave with wavenumber zero. On the other hand, there is parametric excitation process, in which one magnon transform into two magnons which have antiparallel wavenumber vectors. Parametric excitation has been observed by electrical method, but magnetization dynamics in real space have not been observed due to measurement method limitations.
In this study, parametric excitation, a type of nonlinear excitation process, is observed by spin-wave spectroscopy based on time-resolved magneto-optical microscopy which synchronizes the microwave phase and laser pulse timing. Time-resolved magneto-optical imaging is a method to observe magnetization in magnetic materials in real space by measuring the change in polarization of light using the Faraday effect. In the experiment, nonlinear magnetization dynamics is excited by strong microwave in magnetic garnet Bi1Lu2Fe3.4Ga1.6O12 which is known to have a relatively large Faraday rotation angle. The distribution of each spin-wave mode was obtained by Fourier transforming the measured magnetization dynamics. As a result, phase bi-stability, which is unique character of parametric excitation, is observed in real space. In the presentation, we will discuss real space pattern of parametric excitation and its origin.
In this study, parametric excitation, a type of nonlinear excitation process, is observed by spin-wave spectroscopy based on time-resolved magneto-optical microscopy which synchronizes the microwave phase and laser pulse timing. Time-resolved magneto-optical imaging is a method to observe magnetization in magnetic materials in real space by measuring the change in polarization of light using the Faraday effect. In the experiment, nonlinear magnetization dynamics is excited by strong microwave in magnetic garnet Bi1Lu2Fe3.4Ga1.6O12 which is known to have a relatively large Faraday rotation angle. The distribution of each spin-wave mode was obtained by Fourier transforming the measured magnetization dynamics. As a result, phase bi-stability, which is unique character of parametric excitation, is observed in real space. In the presentation, we will discuss real space pattern of parametric excitation and its origin.