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

点击翻译按钮获取中文摘要

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.