NMR observation of steps in the magnetization ofHe3in thin−43He mixture films

Abstract

Nuclear-magnetic-resonance measurements of the magnetization of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ on thin ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixture films show discrete structure as a function of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ coverage over the range 0.0055≤$d_3$≤4 layers at a ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage of 44 μmol/${\mathrm{m}}^2$ for 30≤T≤250 mK in a weakly polarizing 2-T field. A steplike doubling of the magnetization at $d_3$≊0.8 layers and a second less pronounced step at $d_3$≊1.5 layers are ascribed to the population of higher energy levels which evolve as the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ thickens. The magnetization as a function of temperature near the first step is fit by a two-level model with an energy gap $e_{12}$≊1.8 K at the step.