Materials Properties at Very Low Temperatures

总结了过去三年的工作，包括3He中集体模式的动压依赖研究，激发集体模式的新方案，UPt3中的声音传播，极化3He电池的开发，氧化物超导体中的声音传播，新牛津低温恒温器的安装以及薄膜超晶格的超导特性。特别重要的是在UPt3中超声信号衰减的场依赖中声学异常的表征，这可能标志着一种新的相变。他们建议继续研究3He的集体模式光谱，包括极短的路径长度，新的激励方案，非线性效应和极化液体。指出了微波吸收研究在稀释冰箱区域的重要性，并提出了针对集体模式观察的UPt3研究。提出了牛津低温恒温器的顶部加载磁力计改造，再次主要强调UPt3。

The work of the previous three years involving dynamic-pressure- dependent studies of collective modes in 3He, novel schemes to excite collective modes, sound propagation in UPt3, the development of a polarized 3He cell, sound propagation in oxide superconductors, the installation of a new-Oxford cryostat, and the superconducting properties of thin-film superlattices is summarized. Of particular importance was the characterization of an acoustic anomoly in the field dependence of the ultrasonic signal attenuation in UPt3 which may signal a new kind of phase transition. They propose continuing studies of the collective mode spectrum of 3He involving very short path lengths, novel excitation schemes, nonlinear effects, and the polarized liquid. The importance of microwave absorption studies in the dilution refrigerator region is noted and studies of UPt3 directed at the observation of collective modes are proposed. A top loading magnetometer alteration of our Oxford cryostat is proposed, again with the major emphasis on UPt3.