arXiv subjects

Ryo Kainuma

Publications and source records attributed to Ryo Kainuma.

3 recordsLinked to original sources

arXiv2023

Sublattice-selective inverse Faraday effect in ferrimagnetic rare-earth iron garnet

We performed time-resolved pump--probe measurements using rare-earth iron garnet \ce{Gd3/2Yb1/2BiFe5O12} as a two-sublattice ferrimagnet. We measured the initial phases of the magnetic resonance modes below and above the magnetization compensation temperature to clarify the sublattice selectivity of the inverse Faraday effect in ferrimagnets. A comparison of the time evolution of magnetization estimated using the equations of motion revealed that the inverse Faraday effect occurring in ferrimagnetic materials has sublattice selectivity. This is in striking contrast to antiferromagnets, in which the inverse Faraday effect acts on each sublattice identically. The initial phase analysis can be applied to other ferrimagnets with compensation temperatures.

cond-mat.mtrl-sci↗

arXiv2023

Sub-millimeter propagation of antiferromagnetic magnons via magnon-photon coupling

For the realization of magnon-based current-free technologies, referred to as magnonics, all-optical control of magnons is an important technique for both fundamental research and practical applications. Magnon-polariton is a coupled state of magnon and photon in a magnetic medium, expected to exhibit magnon-like controllability and photon-like high-speed propagation. While recent studies have observed magnon-polaritons as modulation of incident terahertz waves, the influence of magnon-photon coupling on magnon propagation properties remains unexplored. This study aimed to observe the spatiotemporal dynamics of coherent magnon-polaritons through time-resolved imaging measurements. BiFeO$_3$ was selected as the sample due to its anticipated strong coupling between magnons and photons. The observed dynamics suggest that antiferromagnetic magnons can propagate over long distances, up to hundreds of micrometers, through strong coupling with photons. These results enhance our understanding of the optical control of magnonic systems, thereby paving the way for terahertz opto-magnonics.

cond-mat.mtrl-sci↗

arXiv2021

Fast acquisition of spin-wave dispersion by compressed sensing

For the realization of magnonic devices, spin-wave dispersions need to be identified. Recently, the time-resolved pump-probe imaging method combined with the Fourier transform was demonstrated for obtaining the dispersions in the lower-wavenumber regime. However, the measurement takes a long time when the sampling rate is sufficiently high. Here, we demonstrated the fast acquisition of spin-wave dispersions by using the compressed sensing technique. Further, we quantitatively evaluated the consistency of the results. Our results can be applied to other various pump-probe measurements, such as observations based on the electro-optical effects.

physics.optics↗