Ultrasonic Investigation of f-Electron Systems

采用超声测量方法研究了含强相关4f电子的稀土化合物的弹性性质。本课题组研制的基于相位比比法的超声仪，对声速变化的检测分辨率高于10^<-7>。在本研究项目中，对1.3GHz以下的高频声波实验进行了许多改进。信号发生器，9087,Racal-Dana，英格兰，扮演着重要的角色。为了产生高频声波，我们开发了ZnO和PVDF（聚偏氟乙烯-聚偏氟乙烯）压电薄膜的制备技术。在过去的两年中，建立了新的低温超声实验装置。连续循环的^3He低温恒温器提供了0.32K的实验。^3He-^4He稀释制冷机现在冷却到8mK。更值得注意的是，3He低温恒温器和稀释冰箱是由东北大学科学测量研究所的机械车间开发的。用超声测量方法研究了稀土化合物中重电子态和价涨落态的特征。需要强调的是，SmB_6和CeNiSn的能隙态是用超声探头检测到的。声学de Haas-van ALphen效应也是本项目的重要课题。对YCu_2、CeCu_2、UB_<12>、LaSb、CeSb、LaSn_3、CeSn_3等介质的声速量子振荡进行了测量。利用稀释制冷机成功观察重电子化合物CeB_6的dHvA效应是本项目的重要进展。在极低温下用超声方法系统地研究重电子系仍然是一个有趣而重要的课题。少

Ultrasonic measurements have been employed for the investigation of the elastic properties of the various rare earth compounds involving the strongly correlated 4f-electrons. The ultrasonic apparatus based on the phase comparison method, which has been developed by our group, reveals the extremely high resolution to detect the sound velocity change better than 10^<-7>. In the present research project, the many improvements for the high frequency sound wave experiments up to 1.3GHz have been performed. The Signal generator, 9087, Racal-Dana, England, plays an important role. For the generation of the high frequency sound waves, we developed the fabrication technique of the piezoelectric film of ZnO and PVDF (polyvinylidene-fluoride). In the last two years, the new apparatuses for the low temperature ultrasonic experiments have been established. The ^3He cryostat of the continuouscirculation provided the experiments at 0.32K. The ^3He-^4He dilution refrigerator is now cooled down to 8mK. … More It Should be noted that the 3He cryostat and the dilution refrigerator were developed by the machine shop in Research Institute for Scientific Measurements of Tohoku University.The characteristic features of the heavy electron and valence fluctuation states in rare earth compounds have been investigated by the ultrasonic measurements. It should be emphasized that the energy gap states in SmB_6 and CeNiSn were detected by the ultrasonic probes. The acoustic de Haas-van ALphen effect was also important subject of the present project. The measurements of the quantum oscillation of sound wave velocity on YCu_2,CeCu_2, UB_<12>, LaSb, CeSb, LaSn_3, CeSn_3 have been performed. The successful observation of acoustic of dHvA effect of the heavy electron compound CeB_6 utilizing the dilution refrigerator was a very important progress in the present project. The systematic investigation of the heavy electron systems with ultrasonic method at very low temperatures in still interesting and important subject. Less