Inelastic neutron scattering study of magnon excitation by ultrasound injection in yttrium iron garnet

Shamoto, Shinichi; Akatsu, Mitsuhiro*; Chang, L.-J.*; Nemoto, Yuichi*; Ieda, Junichi

Applied Physics Letters, 124(11), p.112402_1 - 112402_5, 2024/03

https://doi.org/10.1063/5.0189768

The magnon excitation by ultrasound injection in YFeO is studied by inelastic neutron scattering. Both longitudinal and transverse ultrasound injections enhanced the inelastic neutron scattering intensity.

Crystal-liquid duality driven ultralow two-channel thermal conductivity in -MgAgSb

Li, J.*; Li, X.*; Zhang, Y.*; Zhu, J.*; Zhao, E.*; Kofu, Maiko; Nakajima, Kenji; Avdeev, M.*; Liu, P.-F.*; Sui, J.*; et al.

Applied Physics Reviews (Internet), 11(1), p.011406_1 - 011406_8, 2024/03

https://doi.org/10.1063/5.0173680

Emergence of crack tip plasticity in semi-brittle -Fe

Suzudo, Tomoaki; Ebihara, Kenichi; Tsuru, Tomohito; Mori, Hideki*

Journal of Applied Physics, 135(7), p.075102_1 - 075102_7, 2024/02

https://doi.org/10.1063/5.0178940

Fracture of body centred cubic (bcc) metals and alloys below the ductile-to-brittle transition temperature is brittle. This is theoretically explained by the notion that the critical stress intensity factor of a given crack front for brittle fracture is smaller than that for plasticdeformation; hence, brittle fracture is chosen over plastic deformation. Although this view is true from a macroscopic point of view, such brittle fracture is always accompanied by small-scale plastic deformation in the vicinity of the crack tip, i.e. crack tip plasticity. This short paper investigates the origin of this plasticity using atomistic modeling with a recently developed machine-learning interatomic potential of -Fe. The computational results identified the precursor of crack tip plasticity, i.e. the group of activated atoms dynamically nucleated by fast crack propagation.

Investigation of potential of vacuum-free femtosecond laser sintering for direct printing using silicon carbide nanoparticles without inorganic binder

Kawabori, Tatsuru*; Watanabe, Masashi; Imai, Yoshiyuki; Ueta, Shohei; Yan, X.; Mizoshiri, Mizue*

Applied Physics A, 129(7), p.498_1 - 498_9, 2023/07

https://doi.org/10.1007/s00339-023-06774-z

We investigated a potential of femtosecond laser sintering of silicon carbide (SiC) using the nanoparticles in air. A SiC nanoparticle ink including polyvinylpyrrolidone and ethylene glycol exhibited intense absorption by SiC nanoparticles at the wavelength of 780 nm. The whole of the sintered film patterns from the surface to the bottom underwent significant oxidation at a scanning speed of 1 mm/s, suggesting that the excessive energy irradiation generated silicon oxides. In contrast, the patterns fabricated by laser scanning at a raster pitch of 30 m at which a sintered area was observed at a scanning speed of 5 mm/s, exhibited no significant difference in oxidation of the raw SiC nanoparticles except for the surfaces from 1.72 m. These results indicate that the irradiation of femtosecond laser pulses generated the sintered SiC patterns without additional atmospheric oxidation of the raw materials because of its low heat accumulation. In additions, the dispersant of polyvinylpyrrolidone and ethylene glycol did not affect the sintering by an X-ray photoelectron spectroscopy. This vacuum-free direct printing technique has the potential for additive manufacturing.

Step unbunching phenomenon on 4H-SiC (0001) surface during hydrogen etching

Sakakibara, Ryotaro*; Bao, J.*; Yuhara, Keisuke*; Matsuda, Keita*; Terasawa, Tomoo; Kusunoki, Michiko*; Norimatsu, Wataru*

Applied Physics Letters, 123(3), p.031603_1 - 031603_4, 2023/07

https://doi.org/10.1063/5.0153565

We here report a step unbunching phenomenon, which is the inverse of the phenomenon of step bunching. When a 4H-SiC (0001) surface is annealed at a high temperature, step bunching arises due to the different velocities of the step motion in adjacent steps, resulting in steps with a height of more than several nanometers. We found that the bunched steps, thus, obtained by hydrogen etching in an Ar/H atmosphere were "unbunched" into lower height steps when annealed subsequently at lower temperatures. This unbunching phenomenon can be well explained by the consequence of the competition between energetics and kinetics. Our findings provide another approach for the surface smoothing of SiC by hydrogen etching and may give significant insight into the application of SiC power devices and two-dimensional materials growth techniques in general.

A Large modulation of spin pumping using magnetic phase transitions in single crystalline dysprosium

Yamanoi, Kazuto*; Sakakibara, Yuri*; Fujimoto, Junji*; Matsuo, Mamoru; Nozaki, Yukio*

Applied Physics Express, 16(6), p.063004_1 - 063004_6, 2023/06

https://doi.org/10.35848/1882-0786/acde67

Formation of high-quality SiO/GaN interfaces with suppressed Ga-oxide interlayer via sputter deposition of SiO

Onishi, Kentaro*; Kobayashi, Takuma*; Mizobata, Hidetoshi*; Nozaki, Mikito*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Japanese Journal of Applied Physics, 62(5), p.050903_1 - 050903_4, 2023/05

https://doi.org/10.35848/1347-4065/acd1ca

While the formation of an GaO interlayer is key to achieving SiO/GaN interfaces with low defect density, it can affect the reliability and stability of metal-oxide-semiconductor (MOS) devices if the annealing conditions are not properly designed. In the present study, we aimed to minimize the growth of the GaO layer on the basis of the sputter deposition of SiO on GaN. Synchrotron radiation X-ray photoelectron spectrometry measurements confirmed the suppressed growth of the GaO layer compared with a SiO/GaN structure formed by plasma-enhanced chemical vapor deposition. Negligible GaO growth was also observed when subsequent oxygen annealing up to 600C was performed. A MOS device with negligible capacitance-voltage hysteresis, nearly ideal flat-band voltage, and low leakage current was demonstrated by performing oxygen and forming gas annealing at temperatures of 600C and 400C, respectively.

Magnetization switching process by dual spin-orbit torque in interlayer exchange-coupled systems

Masuda, Hiroto*; Yamane, Yuta*; Seki, Takeshi*; Raab, K.*; Dohi, Takaaki*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Klui, M.*; Takanashi, Koki

Applied Physics Letters, 122(16), p.162402_1 - 162402_7, 2023/04

https://doi.org/10.1063/5.0140328

Shapiro steps in charge-density-wave states driven by ultrasound

Mori, Michiyasu; Maekawa, Sadamichi

Applied Physics Letters, 122(4), p.042202_1 - 042202_5, 2023/01

https://doi.org/10.1063/5.0132454

Direct energy conversion using Ni/SiC Schottky junction in Np and Am gamma ray regions

Fukuda, Tatsuo; Kobata, Masaaki; Shobu, Takahisa; Yoshii, Kenji; Kamiya, Junichiro; Iwamoto, Yosuke; Makino, Takahiro*; Yamazaki, Yuichi*; Oshima, Takeshi*; Shirai, Yasuhiro*; et al.

Journal of Applied Physics, 132(24), p.245102_1 - 245102_8, 2022/12

https://doi.org/10.1063/5.0099136

Direct energy conversion has been investigated using Ni/SiC Schottky junctions with the irradiation of monochromatized synchrotron X-rays simulating the gamma rays of Np (30 keV) and Am (60 keV). From current-voltage measurements, electrical energies were obtained for both kinds of gamma rays. The energy conversion efficiencies were found to reach up to 1.6%, which is comparable to those of a few other semiconducting systems reported thus far. This result shows a possibility of energy recovery from nuclear wastes using the present system, judging from the radiation tolerant nature of SiC. Also, we found different conversion efficiencies between the two samples. This could be understandable from hard X-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements, suggesting the formation of Ni-Si compounds at the interface in the sample with a poor performance. Hence, such combined measurements are useful to provide information that cannot be obtained by electrical measurements alone.