Nuclear magnetic relaxation due to critical effects:35Cl relaxation in NH4Cl and ND4Cl

Publisher Website
Google Scholar
Abstract
The dynamics of critical phenomena in the molecular field approximation are discussed and a calculation of the nuclear spin-lattice relaxation time (T1) for 35Cl nuclei in NH4Cl at temperatures close to the lambda transition point is described. The calculation is based on a linearized Ising model treatment and the approach should be fairly widely applicable. The T1 expression may be expected to fail very close to the critical point. Measurements have been made of the 35ClT1 in NH4Cl and ND4Cl at temperatures both below and above the lambda point. The results for NH4Cl are compared with those obtained by previous workers. The data are analysed using the theoretical expression mentioned above and it is shown that the temperature variation of the order parameter extracted from the results leads to an anomalously low exponent value beta =0.15.