The effect of a magnetic field on fourth sound in 3He

Abstract

The influence of a magnetic field on the propagation o f fourth sound in superfluid 3He is studied. The field and temperature dependences of the average superfluid density Ps/ P and fourth sound Q are measured. The field dependence Of ~s/ p is very different in a porous medium than predicted by Ginzburg-Landau theory applied to bulk liquid. In particular, a magnetic suppression of ~s/ p is observed in the temperature and pressure ranges corresponding to the A phase in bulk liquid. There is strong evidence of a magnetic suppression of T c itself. The measured ps/ P has a slight history dependence in a magnetic feld, but none in zero field. The fourth-sound Q values are compared to the theoretical work of Smith, Jensen, and Wolfle. Quantitative confirmation of their work is problematic.