Pulsed Nuclear Resonance Investigation of the Susceptibility and Magnetic Interaction in Degenerate ³He Films

Abstract

Continuous-wave nuclear resonance measurements have been made recently of the susceptibility and spin—lattice relaxation times on film^1,2 of pure ³He and ³He–⁴He mixtures in the temperature range between 1.5 and 0.4°K for various film thicknesses. In the region investigated the films either were classical, in the sense that their susceptibility followed a Curie law, or showed only small (up ~ 26%) Fermi degeneracy, depending on coverage and temperature. It was shown that the susceptibility was consistent with a statistical layer model in which the first two layers could be considered as magnetically independent of each other and of the rest of the film, and each layer region of the film exhibited the same susceptibility as that of bulk ³He at the same interatomic spacing. Such an interpretation is not necessarily unique, and it is expected to be an approximation. In the present report we show that there are large deviations from this model at lower temperatures down to 50 m°K, in such a direction as to indicate a lower Fermi temperature in the real film than in the model, or a larger ferromagnetically inclined exchange interaction.

This work was supported by the Science Research Council and by the U.S. Air Force Office of Scientific Research through the European Office of Aerospace Research (Grant EOOAR 68-0023).