NMR study of liquid to solid transition in a glass forming metallic system

摘要

Quadrupolar spin-lattice relaxation effect was used to study the temperature dependence of the correlation of electric field gradient (EFG) observed by Cu-63 and Cu-65 NMR in the liquid and supercooled liquid states of Pd43Cu27Ni10P20 metallic glass forming system. The correlation time of EFG was shown to have a dramatic temperature dependence that cannot be accounted for by available theory. Analyzed in the context of mode coupling theory (MCT), it is shown that the correlation time of EFG follows the scaling equation of MCT and reveals a T-c, the critical temperature of MCT, at 700 K. Other NMR techniques such as chemical exchange line narrowing and stimulated echo pulse sequences were used to study motion of P-31 at lower temperatures. Combined together, these techniques cover the whole range of liquid to solid transition. By comparing the NMR results with data obtained by other techniques, a decoupling of motion for different types of atoms is revealed starting from T-c and below. This essentially demonstrates a transition from liquidlike to solidlike motion at T-c as predicted by MCT. (c) 2008 American Institute of Physics.