NMR Studies on 3He-3He and 3He-4He tunneling motions in solid 3He-4He mixtures

Abstract

Helium-3 nuclear spin relaxation times T 1, T 2, and T 1ϱhave been measured for 3He-4He solid mixtures at the exchange plateau region (~0.5K). The 3He concentrations X 3of the samples were 7.2, 2.9, 1.8, 1.4, 0.67, 0.65, and 0.22%, and their molar volumes varied between 19.9 and 20.9cm3/mole in hcp phase. The spectral density function J(Ω) for dipolar field fluctuations was determined in the low-frequency branch from T 1ϱmeasurements and in the high-frequency branch from conventional T 1measurements. It was found that J(Ω) is given by J(ω) = cJ(ω)|3−4 + (1−c)J(ω)|3−3, where J(Ω)|3−4 is the spectral density function due to the 3He-4He tunneling motions, and J(Ω)|3−3 is that due to the 3He-3He tunneling motions. Using the Torrey theory, the correlation frequency of the 3He-4He tunneling motions was evaluated from T 1ϱdata, and was found to be in good agreement with Landesman 's theory.