ONE-DIMENSIONAL BEHAVIOR OF FERROELASTIC DOMAIN ARRAYS IN NEODYMIUM PENTAPHOSPHATE

Domain structures in ferroelastic neodymium pentaphosphate NdP5O14 of small a and b dimensions have been observed to be nearly periodic doma in arrays of quasi-one-dimension sandwiched by parallel domain walls a long the (001) lattice plane. Based on a continuous order-parameter pr ofile along the wall normal, a positive temperature-dependent wall ene rgy was obtained from Landau's theory of second-order phase transition s. Then a one-dimensional spin system, with the spins corresponding to the shear strains of the two orientation states of NdP5O14, has been developed to describe statistically the effect of thermal energy excit ing the fluctuation of the wall number. The theoretical deductions wer e well consistent with the actual drastic increase of walls on approac hing the phase transition temperature and the dynamical behavior of th e domains in external stress fields.