1998 Fiscal Year Final Research Report Summary
Microwave Radiation from YIG Magnons
| Project/Area Number |
09640435
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
YAMAZAKI Hitoshi Okayama University, Faculty of Science Professor, 理学部, 教授 (40013495)
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| Co-Investigator(Kenkyū-buntansha) |
MINO Michinobu Okayama University, Faculty of Science Research Associate, 理学部, 助手 (30222326)
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| Project Period (FY) |
1997 – 1998
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| Keywords | MAGNON / SPIN-WAVE / PARALLEL PUMPING / MICROWAVE RADIATION / YIG / PARAMETRIC EXCITATION |
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| Research Abstract |
Unstable growth of particular magnon can be generated by nonlinear excitation (parametric excitation) with high microwave power. Those magnons in the nonequilibrium state are scattered to other magnons, which have different frequencies and wave_ vectors. Those magnons occasionally radiate microwave. Magnon interactions or magnon condensation state can be studied by detecting microwave radiation from the nonequilibrium magnon system.
Nonequilibrium magnons excited in a single crystal of ferrimagnet YIG (Yttrium Iron Garnet), which was placed in a microwave cavity, nonlinearly couples with microwave photon with configuring magnon-photon nonlinearly coupled oscillator mode. Those coupled modes were studied by means of additional weak microwave signal. Theoretical calculations, which consider coupled systems of resonator mode and magnetic sample, are found to be in good agreement with the experimental data.
Microwave radiation was detected from a sphere single crystal of YIG with applying both static and microwave magnetic field parallel to the [111] axis, easy magnetization axis. A disk sample was also used with applying magnetic fields parallel to the sample surface, which is perpendicular to the [111] axis. The frequencies of pumping microwave were 9.5 and 15.4 GHz. Radiated microwave was detected by a small pick-up coil wounded around a sample and analyzed by a microwave spectrum analyzer. The intensity of radiated microwave was measured as a function of time after the end of pulse pumping. As a result, relaxation time of magnon is directly determined as 19 p s which is in agreement with spin-wave relaxation time measured by other experiments.
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