High frequency NMR in bcc solid 3He

Abstract

We report a comprehensive experimental study of the spin lattice relaxation in bulk bcc solid 3He at high Larmor frequency (200 MHz). The various temperature regimes for T 1 are investigated in connection with the results of low field experiments. At high temperature the modulation of the dipolar interaction by vacancies and atomic exchage motions gives a good account of the experimental data thus providing an answer to a question raised by several experiments: at high magnetic field (6.2T) the correlation function for the modulation of the dipolar interaction by the exchange of 3He atoms remains well described by a Lorentzian function as deduced from low field experiments. At low temperature a plateau is observed and explained by the presence of dislocations in the solid, a model consistent with both low and high field experiments. The influences on T 1 of the 3He 4He phase separation in solid and of the melting of the solid at temperatures lower than the minimum of the melting curve are discussed using this model.