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539 results on '"Mitsudo S."'

1. Electrical detection of antiferromagnetic dynamics in Gd-Co thin films by using a 154-GHz gyrotron irradiation

Author

Funada, S., Ishikawa, Y., Kimata, M., Hayashi, K., Sano, T., Sugi, K., Fujii, Y., Mitsudo, S., Shiota, Y., Ono, T., and Moriyama, T.

Subjects
Condensed Matter - Materials Science, Physics - Applied Physics
Abstract

THz magnetization dynamics is a key property of antiferromagnets as well as ferrimagnets that could harness the THz forefront and spintronics. While most of the present THz measurement techniques are for bulk materials whose sensitivities rely on the volume of the material, measurement techniques suitable for thin films are quite limited. In this study, we explored and demonstrated electrical detection of the antiferromagnetic dynamics in ferrimagnetic Gd-Co thin films by using a 154 GHz gyrotron, a high-power electromagnetic wave source. Captured resonant modes allow us to characterize the peculiar magnetization dynamics of the Gd-Co around the net angular momentum compensation. As the gyrotron frequency is scalable up to THz, our demonstration can be an important milestone toward the THz measurements for antiferro- and ferri- magnetic thin films.

Published
2023

2. Formation of porous clay ceramic using sago waste ash as a prospective additive material with controllable milling

Author

Aripin H., Mitsudo S., Rahmat B., Tani S., Sako K., Fujii Y., Kikuchi K., Saito T., Idehara T., and Sabchevski S.

Subjects
unglazed ceramic tile, sago waste, clay, sintering temperature, milling time, water absorption, hardness, Chemical technology, TP1-1185
Abstract

A novel type of ceramic material was produced by mixing sago waste ash from the sago processing industry in Indonesia with clay. The composition was prepared by adding 50 %wt amount of sago waste into the clay, then a series of samples was milled for 6 h, 12 h, 24 h and 48 h, respectively. The samples were dry pressed and sintered at temperatures ranging from 800°C to 1200°C. The influence of the sintering temperature and the milling time on bulk density, firing shrinkage, water adsorption, and hardness was studied in detail. The results demonstrate that the low water absorption of less than 0.5% and the highest hardness of 5.82 GPa were obtained for the sample sintered at 1100°C and milled for 48 h. The investigation of the absorptive properties of such ceramics indicates that they could be recommended as a promising material for manufacturing of unglazed floor tiles.

Published
2014
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3. Microscopic control of $^{29}$Si nuclear spins near phosphorus donors in silicon

Author

Järvinen, J., Zvezdov, D., Ahokas, J., Sheludyakov, S., Vainio, O., Lehtonen, L., Vasiliev, S., Fujii, Y., Mitsudo, S., Mizusaki, T., Gwak, M., Lee, SangGap, Lee, Soonchil, and Vlasenko, L.

Subjects
Physics - Atomic and Molecular Clusters, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We demonstrate an efficient control of $^{29}$Si nuclear spin orientation for specific lattice sites near $^{31}$P donors in silicon crystals at temperatures below 1 K and in high magnetic field of 4.6 T. Excitation of the forbidden electron-nuclear transitions leads to a pattern of narrow holes and peaks in the ESR lines of $^{31}$P. The pattern originates from dynamic polarization the $^{29}$Si nuclear spins near the donors via the solid effect. This method can be used for initialization of qubits based on $^{29}$Si nuclear spins in the all-silicon quantum computer. In comparison, polarization of $^{29}$Si performed by pumping the allowed ESR transitions, did not create any patterns. Instead, a single narrow spectral hole was burnt in the ESR line. The difference is explained by a rapid spin diffusion during the microwave pumping of the allowed transitions.

Published
2014
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4. Efficient Dynamic Polarization of Phosphorus Nuclei in Silicon in Strong Magnetic Fields and Low Temperatures

Author

Järvinen, J., Zvezdov, D., Ahokas, J., Sheludyakov, S., Vainio, O., Lehtonen, L., Vasiliev, S., Fujii, Y., Mitsudo, S., Mizusaki, T., Gwak, M., Lee, SangGap, Lee, Soonchil, and Vlasenko, L.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We demonstrate that the dynamic nuclear polarization (DNP) of phosphorus donors in silicon can be very effective in a magnetic field of 4.6 T and at temperatures below 1 K. The DNP occurs due to the Overhauser effect following a cross relaxation via the forbidden flip-flop or flip-flip transitions. Nuclear polarization values $P>0.98$ were reached after 20 min of pumping with 0.4 $\mu$W of microwave power. We evaluated that the ratio of hyperfine state populations increased by three orders of magnitude after 2 hours of pumping, and an extremely pure nuclear spin system containing $<10^{-11}$ of the other spin state can be created. An inverted DNP has been obtained by pumping the low field ESR line of P followed by the flip-flip cross relaxation. This transition has much smaller relaxation rate and required substantially longer pumping times. We found that the nuclear polarization dynamics deviates substantially from a simple exponential function. The evolution of the polarization is characterized by two time constants $T^{'}_{ac}\approx$15 s in the beginning, and $T^{"}_{ac}\approx$1100 s for long pumping time. Temperature dependence of the nuclear relaxation rate of $^{31}$P was studied down to 0.75 K, below which the relaxation time became too long to be measured. The nuclear polarization followed a bi-exponential time dependence during relaxation. We suggest that the non-exponential behavior of DNP dynamics and the subsequent relaxation is mediated by the nuclei of $^{29}$Si surrounding $^{31}$P donors, which affect the transition probabilities of the forbidden cross-relaxation processes.

Published
2014
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31. Design of a Large Orbit Gyrotron with a Permanent Magnet System

Author

Zapevalov, V., Idehara, T., Sabchevski, S., Ohashi, K., Manuilov, V., Glyavin, M., Kornishin, S., Kuftin, A., Lygin, V., Malygin, O., Moiseev, M., Pavel'ev, A., Tzalolikhin, V., Zavolsky, N., Kobayashi, H., Yokoyama, T., Ogawa, I., Mitsudo, S., Kanemaki, T., Iwata, Y., and Hoshizuki, H.

Published
2003
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45. BORON CARBIDE CERAMICS SINTERING BY USING 24 GHz COMPACT GYROTRON

Author

Mitsudo, S., primary, Hoshizuki, H., additional, Matsuura, K., additional, Saji, T., additional, Idehara, T., additional, Glyavin, M., additional, Eremeev, A., additional, Honda, T., additional, Iwai, Y., additional, Nishi, H., additional, Kitano, A., additional, and Ishibashi, J., additional

Published
2005
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49. Cu-Ag alloy Bitter type magnet for repeating pulsed field

Author

Motokawa, M., Nojiri, H., Mitsudo, S., Arai, M., Ubukata, K., Fujita, M., Arakawa, T., and Inamura, Y.

Subjects
Superconducting magnets -- Design and construction, Business, Electronics, Electronics and electrical industries
Abstract

Cu-Ag alloy is used for the repeating pulsed field magnets. It is found that fields up to 22 T or more will be available for this purpose instead of 16 T which is obtained with normal copper magnet used at present. This result is a big advantage for neutron diffraction experiments.

Published
1996

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