ON THE PHASE TRANSITION SEQUENCE IN DEUTERATED BETAINE CALCIUM CHLORIDE DIHYDRATE UNDER HYDROSTATIC PRESSURE

摘要

An elastic neutron scattering study of deuterated betaine calcium chloride dihydrate under hydrostatic pressure is presented. It is shown that a previous phenomenological model based on a one-dimensional order parameter P, and involving a term of the form P-2(delta P/delta z)(2) remains adequate to account satisfactorily for the effects of the hydrostatic pressure. From the study of the temperature dependence of the integrated intensity of the satellites it is inferred that the critical exponent beta related to the primary order parameter is close to 0.5 for 2.9 x 10(8), 3.4 x 10(8), and 4 x 10(8) Pa. [References: 27]