NMR observation of steps in the magnetization of 3He in thin 3He-4He mixture films.

Nuclear-magnetic-resonance measurements of the magnetization of $^{3}\mathrm{He}$ on thin $^{3}\mathrm{\ensuremath{-}}^{4}$He mixture films show discrete structure as a function of $^{3}\mathrm{He}$ coverage over the range 0.0055\ensuremath{\le}${d}_{3}$\ensuremath{\le}4 layers at a $^{4}\mathrm{He}$ coverage of 44 \ensuremath{\mu}mol/${\mathrm{m}}^{2}$ for 30\ensuremath{\le}T\ensuremath{\le}250 mK in a weakly polarizing 2-T field. A steplike doubling of the magnetization at ${d}_{3}$\ensuremath{\approxeq}0.8 layers and a second less pronounced step at ${d}_{3}$\ensuremath{\approxeq}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 ${e}_{12}$\ensuremath{\approxeq}1.8 K at the step.