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論文

Strongly coupled spin waves and surface acoustic waves at room temperature

Hwang, Y.*; Puebla, J.*; 近藤 浩太*; Gonzalez-Ballestero, C.*; 一色 弘成*; S$'a$nchez Mu$~n$oz, C.*; Liao, L.*; Chen, F.*; Luo, W.*; 前川 禎通*; et al.

Physical Review Letters, 132(5), p.056704_1 - 056704_7, 2024/01

 被引用回数:14 パーセンタイル:96.23(Physics, Multidisciplinary)

Here, we report the observation of strong coupling between magnons and surface acoustic wave (SAW) phonons in a thin CoFeB film constructed in an on-chip SAW resonator by analyzing SAW phonon dispersion anticrossings. We employ a nanostructured SAW resonator design that, in contrast to conventional SAW resonators, allows us to enhance shear-horizontal strain. Crucially, this type of strain couples strongly to magnons. Our device design provides the tunability of the film thickness with a fixed phonon wavelength, which is a departure from the conventional approach in strong magnon-phonon coupling research. We detect a monotonic increase in the coupling strength by expanding the film thickness, which agrees with our theoretical model. Our work offers a significant way to advance fundamental research and the development of devices based on magnon-phonon hybrid quasiparticles.

論文

Valley-selective phonon-magnon scattering in magnetoelastic superlattices

Liao, L.*; Puebla, J.*; 山本 慧; Kim, J.*; 前川 禎通*; Hwang, Y.*; Ba, Y.*; 大谷 義近*

Physical Review Letters, 131(17), p.176701_1 - 176701_6, 2023/10

 被引用回数:8 パーセンタイル:81.90(Physics, Multidisciplinary)

Phonons and magnons are engineered by periodic potential landscapes in phononic and magnonic crystals, and their combined studies may enable valley phonon transport tunable by the magnetic field. Through nonreciprocal surface acoustic wave transmission, we demonstrate valley-selective phonon-magnon scattering in magnetoelastic superlattices. The lattice symmetry and the out-of-plane magnetization component control the sign of nonreciprocity. The phonons in the valleys play a crucial role in generating nonreciprocal transmission by inducing helical strains that couple with the magnons. The transmission spectra show a nonreciprocity peak near a transmission gap, matching the phononic band structure. Our results open the way for manipulating valley phonon transport through periodically varying magnon-phonon coupling.

論文

Perspectives on spintronics with surface acoustic waves

Puebla, J.*; Hwang, Y.*; 前川 禎通*; 大谷 義近*

Applied Physics Letters, 120(22), p.220502_1 - 220502_9, 2022/05

 被引用回数:36 パーセンタイル:93.59(Physics, Applied)

Surface acoustic waves (SAWs) are elastic waves propagating on the surface of solids with the amplitude decaying into the solid. The well- established fabrication of compact SAW devices, together with well-defined resonance frequencies, places SAWs as an attractive route to manipulate the magnetization states in spintronics, all of which is made possible by the magnetostriction and magnetoelastic effects. Here, we review the basic characteristics of SAW devices and their interaction out-of-resonance and in-resonance with the magnetization in thin films. We describe our own recent results in this research field and closely related works and provide our perspectives moving forward.

論文

Spin-flop phase in a honeycomb antiferromagnet Mn$$_{0.84}$$Mg$$_{0.16}$$TiO$$_{3}$$

社本 真一; 山内 宏樹; 池内 和彦*; Lee, M. K.*; Chang, L.-J.*; Garlea, V. O.*; Hwang, I. Y.*; Lee, K. H.*; Chung, J.-H.*

Journal of the Physical Society of Japan, 90(9), p.093703_1 - 093703_4, 2021/09

 被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)

ハニカム格子反強磁性体Mn$$_{0.84}$$Mg$$_{0.16}$$TiO$$_{3}$$の5T磁場下でのスピンフロップ相の磁気構造を弾性散乱と非弾性散乱を相補的に用いることで、初めて提案した。

論文

Spin wave excitations in honeycomb antiferromagnet MnTiO$$_{3}$$

Hwang, I. Y.*; Lee, K. H.*; Chung, J.-H.*; 池内 和彦*; Garlea, V. O.*; 山内 宏樹; 赤津 光洋*; 社本 真一

Journal of the Physical Society of Japan, 90(6), p.064708_1 - 064708_6, 2021/06

 被引用回数:5 パーセンタイル:39.17(Physics, Multidisciplinary)

ハニカム格子反強磁性体MnTiO$$_{3}$$のスピン波を調べ、スピン間の交換相互作用を正確に求めた。

論文

Programmable synthesis of silver wheels

Kwon, H.*; Pietrasiak, E.*; 大原 高志; 中尾 朗子*; Chae, B.*; Hwang, C.-C.*; Jung, D.*; Hwang, I.-C.*; Ko, Y. H.*; Kim, K.*; et al.

Inorganic Chemistry, 60(9), p.6403 - 6409, 2021/05

 被引用回数:0 パーセンタイル:0.00(Chemistry, Inorganic & Nuclear)

The synthesis of sandwich-shaped multinuclear silver complexes with planar penta- and tetranuclear wheel-shaped silver units and a central anion is reported, along with complete spectroscopic and structural characterization. An NMR mechanistic study reveals that silver complexes were formed in the following order: 2Ag $$rightarrow$$ 3Ag$$^{rm H2O}$$ $$rightarrow$$ 5Ag$$^{rm OH}$$ $$rightarrow$$ 4Ag$$^{rm OH}$$. The central hydroxides in 4Ag$$^{rm OH}$$ and 5Ag$$^{rm OH}$$ exhibit exotic physical properties due to the confined environment inside the complex. The size of these silver wheels can be tuned by changing the central anion or extracting/adding one silver atom. This study provides the facile way to synthesize discrete wheel-shaped multinuclear silver complexes and provides valuable insights into the dynamics of the self-assembly process.

論文

Systematic changes of the electronic structure of the diluted ferromagnetic oxide Li-doped Ni$$_{1-x}$$Fe$$_x$$O with hole doping

小林 正起*; Hwang, J. I.*; Song, G.*; 大木 康弘*; 滝沢 優*; 藤森 淳; 竹田 幸治; 藤森 伸一; 寺井 恒太*; 岡根 哲夫; et al.

Physical Review B, 78(15), p.155322_1 - 155322_4, 2008/10

 被引用回数:6 パーセンタイル:29.16(Materials Science, Multidisciplinary)

The electronic structure of Li-doped Ni$$_{1-x}$$Fe$$_x$$O has been investigated using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The Ni $$2p$$ core-level PES and XAS spectra were not changed by Li doping. In contrast, the Fe$$^{3+}$$ intensity increased with Li doping relative to the Fe$$^{2+}$$ intensity. However, the increase of Fe$$^{3+}$$ is only $$sim 5%$$ of the doped Li content, suggesting that most of the doped holes enter the O $$2p$$ and/or the charge-transferred configuration Ni $$3d^8underline{L}$$. The Fe $$3d$$ partial density of states and the host valence-band emission near valence-band maximum increased with Li content, consistent with the increase of electrical conductivity. Based on these findings, percolation of bound magnetic polarons is proposed as an origin of the ferromagnetic behavior.

論文

Phase change observed in ultrathin Ba$$_{0.5}$$Sr$$_{0.5}$$TiO$$_3$$ films by in situ resonant photoemission spectroscopy

Lin, Y.-H.*; 寺井 恒太*; 和達 大樹*; 小林 正起*; 滝沢 優*; Hwang, J. I.*; 藤森 淳; Nan, C.-W.*; Li, J.-F.*; 藤森 伸一; et al.

Applied Physics Letters, 90(22), p.222909_1 - 222909_3, 2007/05

AA2007-0754.pdf:0.58MB

 被引用回数:8 パーセンタイル:32.64(Physics, Applied)

パルスレーザー堆積法によりNbをドープしたSrTiO$$_3$$(100)基板上にBa$$_{0.5}$$Sr$$_{0.5}$$TiO$$_3$$のエピタキシャル薄膜を作製し、室温と低温で価電子帯のTi 2p$$rightarrow$$3dの共鳴光電子分光スペクトルを測定した。その結果膜厚が2.8nm($$sim$$7ML)と2.0nm($$sim$$5ML)の間で大きな違いがみられ、強誘電転移の臨界膜厚が2.0-2.8nmの範囲にあることがわかった。

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