A NMR Study of the Statics and Dynamics of Thin Helium Films

The results of nuclear magnetic resonance (NMR) on thin ^3{He} -^4He mixture films at temperatures 24mK <=q T <=q 650mK which are adsorbed to Nucleopore are reported. The nuclear magnetic susceptibility, the relaxation times T_1 and T_2, and the spin diffusion coefficient, D, were measured used pulsed NMR techniques in a 2 Tesla field. The ^4He coverages investigated ranged from 0.137 <=q n_4 <=q 0.534 atoms A^2 with a fixed submonolayer ^3He coverage of 0.00746 <=q n_3 <=q 0.00749 atoms A^2. At n _4 = 0.391 atoms/A^2 measurements were taken with the ^3He coverage ranging 0.00749 <=q n_3 <=q 0.0179 atoms/A^2. We present the ^3He magnetization as a function of the ^4He coverage. The magnetization is degenerate for temperatures below the Fermi temperature, T_{F}, and from the degenerate magnetization the hydrodynamic mass over a range of ^4He coverages is obtained. Variational and density functional descriptions of the film are considered. The diffusion data are seen to rise rapidly, from 10^{-8} to 10^{-3} {cm}^2/sec, as the ^4 He coverage is increased from 0.19 to 0.39 atoms/A ^2, a range of just 2.5 layers. For T < T_{F} the temperature dependence of a degenerate Fermi gas is not seen; D not= T^{-2}. For all coverages T_1 is two orders of magnitude larger than T_2 . Two regimes are seen. For coverages n _4 < 0.23 the temperature dependence of T _1 and T_2 are consistent with omegatau_ {c} gg 1. A signature of the completion of the second layer of the ^4He is seen in T_{1}. For coverages n_4 > 0.23, omega tau_{c} << 1 and the temperature dependence correlates with the superfluid areal density. Activated behavior is seen which probes higher bound states of the ^3He in the ^4He film.