Dynamics of the 1st order phase transition between the nuclear ordered phases of solid 3He Original Research Article

Dynamics of the 1st order phase transition between the U2D2 and the high field phases (HFP) was studied by field-cycling method between these phases by using ultra low temperature magnetic resonance imaging (ULT-MRI). Single Crystal of U2D2 3He was produced at the bottom of compressional cell in superfluid 3He-B at about 0.5 mK. Domain distribution in the U2D2 crystal was examined by ULT-MRI. We have measured the NMR signal intensity to extract the time-evolution of the HFP, after the static magnetic field was swept quickly through the critical field BC1 and was stayed at B=BC1+ΔB. The volume concentration of the U2D2 decreased exponentially in time during the early stage of the phase transition. The rate constant depended positively on ΔB. After the phase transition to the HFP was completed, the static field decreased through BC1 and was fixed at B=BC1−ΔB. The observed rate constant was similar to the value in the opposite direction with identical ΔB. This exponential evolution and ΔB dependence of its rate suggest that the early stage of the phase transition is controlled by the nucleation process.