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Detection of the Spin Wave in UUDD Phase of Solid 3He.

固体 3He UUDD 相中自旋波的检测。

基本信息

批准号：
02640245
负责人：
SAWADA Anju
金额：
$ 1.15万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02640245/
关键词：
Solid 3He Nuclear Spin Exchange Interaction Spin Wave Nuclear Magnetic Order Pressure at Constant Volume Nuclear Demagnetization First Order Phase Transition 消磁装置固体^3He、核スピン、交換相互作用、一次相転移、スピン波、定積圧力、核磁気秩序、消磁装置、核断熱消

项目摘要

bcc Solid 3He have been attracted much attention, in particular because of the simplest magnetic system. Unexpectedly the nuclear magnetic properties cleared from the experiments are very complicated and very interesting. Theoretically, it is thought that the main terms of the interaction are the ordinary pair exchange, and the unusual three- and four-body exchange. The experimental results of NMR, pressure and specific heat have established that two magnetic ordered phases exist in bcc solid ^3He : a low field antiferromagnetic phase(LFP)for temperatures lower than lmK, and a high field magnetically ordered phase(HFP)for field greater than 0.4T. The transitions to the LFP from the paremagnetic phase(PP)or the HFP have been clarified as first order. However, the order of the HFP-PP transition is still controversial. The melting pressure of ^3He was measured in magnetic field. The phase transitions of solid ^3He were determined by the anomaly of the melting curves during the temperature and the magnetic field sweep. With thus determined B-T phase diagram, the slope of the transition line near the triple point suggests the first order transition of the PP to the HFP transition. However, any trace of the latent heat was not observed within our experimental accuracy.We tried to determine the order of the transition from the measurements of the pressure at constant volume sweeping the magnetic field. The experimental results first indicated the pressure jump with the phase transition and established the first order phase transition. Also, the phase line between LFP and HFP have been measured, and indicated that the critical field depend on the fourth power of the critical field. This result mean that almost excitations are the antiferromagnetic spin waves in both ordered phases. The phase line between LFP and PP is dominated by free energy change of the magnetic field, and indicate that the critical field depend on the square root of the change of the critical field.

由于它具有最简单的磁性系统，因此受到了广泛的关注。出乎意料的是，从实验中得到的核磁性质是非常复杂和有趣的。理论上，人们认为相互作用的主要项是普通的对交换，以及不寻常的三体和四体交换。核磁共振、压力和比热的实验结果表明，bcc固体^3He中存在两种磁性有序相：温度低于lmK时的低场反铁磁相（LFP）和场大于0.4T时的高场磁性有序相（HFP）。从对磁相（PP）或HFP到LFP的转变已被澄清为一阶。然而，HFP-PP过渡的顺序仍然存在争议。测量了^3He在磁场中的熔化压力。固体^3He的相变是通过温度和磁场扫描过程中熔化曲线的异常来确定的。由此确定的B-T相图，三相点附近过渡线的斜率表明PP向HFP的一级过渡。然而，在我们的实验精度范围内，没有观察到任何潜热的痕迹。我们试着通过测量恒定体积下扫过磁场的压力来确定转变的顺序。实验结果首次表明了压力随相变而跃变，建立了一阶相变。同时测量了LFP和HFP之间的相线，表明临界场依赖于临界场的四次幂。这一结果意味着在两个有序相中几乎激发都是反铁磁自旋波。LFP和PP之间的相线以磁场的自由能变化为主，表明临界场取决于临界场变化的平方根。