SLOW GROWTH OF HE-3-B INTO HYPERCOOLED HE-3-A

We report observations of the first-order phase transition between the two superfluid phases of He-3. We supercool a long cylindrical sample of the higher-temperature A phase in a magnetic field in a simple dc magnetometer. We then introduce B phase at one end of the sample and observe its growth into the supercooled A phase via the magnetometer signal. For temperatures above a certain value, the phase interface travels up the tube with a nearly time-independent velocity, whose temperature dependence is in reasonable agreement with theory. We also investigate the dependence of this velocity on tube diameter and magnetic field. Our measured values of the difference between A phase and B phase magnetization agree with previous dynamic (NMR) measurements. We also derive thermodynamic data on the AB transition from the measurements of magnetization difference and the dependence of the transition temperature on magnetic field.