Decomposition of weak hcp solutions 3He–4He and magnetic properties of decomposed samples
Abstract
The kinetics of phase separation of weak hcp solutions 3He–4He with initial concentrations of 3He equal to 0.5±0.1 and 1.2±0.2% under sample pressures 3.5 – 3.8 MPa before the decomposition is reported. An NMR technique is developed for a prompt control of the phase separation process. To accelerate the decomposition of the metastable phase, samples were subjected to thermal cycling at temperatures below 100 mK. Pulsed NMR technique was used to measure the magnetic susceptibility of 3He nuclei as well as spin–lattice (T1) and spin–spin (T2) relaxation times in three samples of decomposed solid solution with an initial concentration 0.5% 3He under pressures of 3.53, 3.71 and 3.78 MPa. At temperatures above 10 mK, the Curie–Weiss law is obeyed. The Weiss constant for two of the three investigated samples is found to be 2–3 times higher than the characteristic values for bulk bcc 3He of the same density. Below 10 mK, the magnetic susceptibility is found to deviate from the Curie–Weiss dependence. In one of the samples, a broad peak is observed in the temperature dependence of susceptibility at a temperature of 3 mK. The magnetic phase ordering was not detected in the investigated samples right up to a temperature of 0.7 mK.