Pressure dependence of theA-Bphase transition temperature in superfluid3Hein 1.1-μm slab geometry

Abstract

To investigate the size effects of superfluid ${}^3\mathrm{He}$ in a slab geometry, we made a sample cell which has very uniform 1.1 μm spacing by stacking 440 films, where the static magnetic field for NMR was fixed parallel to the film surface. We performed cw NMR experiments in the superfluid state and observed the jump of resonance frequency shift at 10, 20, 24, and 27 bar. We attributed these phenomena to the A-B phase transition which occurs in 1.1 μm slab spacing at the temperature $T_{\mathrm{AB}}\left(1.1\mathrm{}\mu \mathrm{m}\right).\mathrm{}$ The A-B phase transition temperatures were suppressed by about 15% from those of the bulk liquid at higher pressures. When we coated the film surface with some ${}^4\mathrm{He}$ layers, we observed that the $T_{\mathrm{AB}}\left(1.1\mathrm{}\mu \mathrm{m}\right)$ became higher with increasing surface ${}^4\mathrm{He}$ layers.