Crystallization and melting of spin-polarized He-3

The melting and growth of He-3 crystals, spin-polarized by an external magnetic field, are different in nature depending on whether the temperature is higher or lower than the characteristic ordering temperatures in the crystal (the Neel temperature T-N) and in the liquid (the superfluid transition temperature T-c). In the high-temperature region (T greater than or equal to T-N, T-c) the liquid which appears upon melting has a high nonequilibrium spin density. In the low-temperature region (T << T-N, T-c) the melting and growth are accompanied by spin supercurrents both in the liquid and in the crystal in addition to mass supercurrents in the liquid. The crystallization waves at the liquid-solid interface should exist in the low-temperature region. With increasing magnetic field the waves change in nature, because the spin currents begin to play a. dominant role. The wave spectrum becomes linear with a velocity inversely proportional to the magnetic field. The attenuation of the waves at low enough temperatures is mainly due to the interaction of the moving crystal-liquid interface with thermal spin waves in the crystal. The waves could be weakly damped at temperatures below a few hundreds microkelvins.