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Microwave Radiation from YIG Magnons

YIG 磁振子的微波辐射

基本信息

批准号：
09640435
负责人：
YAMAZAKI Hitoshi
金额：
$ 2.3万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640435/
关键词：
MAGNON SPIN-WAVE PARALLEL PUMPING MICROWAVE RADIATION YIG PARAMETRIC EXCITATION

项目摘要

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.

高微波功率的非线性激励（参量激励）可以产生特定磁振子的不稳定生长。那些处于非平衡态的磁振子被散射到其他具有不同频率和波矢的磁振子。这些磁振子偶尔会辐射微波。通过检测来自非平衡磁振子系统的微波辐射，可以研究磁振子相互作用或磁振子凝聚态。放置在微波腔中的亚铁磁体YIG（钇铁石榴石）单晶中激发的非平衡磁振子与微波光子非线性耦合，配置磁子-光子非线性耦合振荡模式。通过附加微弱微波信号来研究这些耦合模式。考虑谐振器模式和磁性样品耦合系统的理论计算与实验数据吻合良好。通过施加平行于[111]轴（易磁化轴）的静态磁场和微波磁场，从YIG球形单晶中检测到微波辐射。还使用圆盘样品来施加平行于样品表面的磁场，该表面垂直于[111]轴。泵浦微波的频率为9.5和15.4 GHz。通过缠绕在样品周围的小型拾波线圈检测辐射的微波，并通过微波频谱分析仪进行分析。在脉冲泵浦结束后测量辐射微波的强度作为时间的函数。结果，直接确定磁振子弛豫时间为19 p s，与其他实验测量的自旋波弛豫时间一致。