Effect of magnetic scattering on the superfluid transition of He3 in nematic aerogel

Abstract

We present the results of high magnetic field experiments in pure $^{3}\mathrm{He}$ (in the absence of $^{4}\mathrm{He}$ coverage) in nematic aerogel. In this case the aerogel strands are covered with few atomic layers of solid paramagnetic $^{3}\mathrm{He}$, which enables the spin-exchange mechanism for $^{3}\mathrm{He}$ quasiparticles scattering. Our earlier NMR experiments showed that in low fields, instead of the polar phase, the $A$ phase is expected to emerge in nematic aerogel. We use a vibrating wire resonator with the sample of aerogel attached to it and measure temperature dependencies of resonance properties of the resonator at different magnetic fields. A superfluid transition temperature of $^{3}\mathrm{He}$ in aerogel, obtained from the experiments, increases nonlinearly in applied magnetic field. And this increase is suppressed compared with that for the bulk ${A}_{1}$ phase, which we attribute to an influence of the magnetic scattering channel, previously considered theoretically for the case of $^{3}\mathrm{He}$ confined in isotropic silica aerogel. However, we observe the essential quantitative mismatch with theoretical expectations.