W0369

NMR Detection of Dynamics and Crystallization in Metallic Supercooled Liquids and Glasses. Lilong Li and Yue Wu, Department of Physics and Astronomy and Curriculum in Applied and Materials Sciences, Univ. of North Carolina, Chapel Hill, NC 27599-3255.

Nuclear magnetic resonance (NMR) is a local probe of atomic structures and dynamics and is an important complementary tool to diffraction measurements, especially in the study of disordered systems. We will discuss several examples of its applications in the study of bulk metallic glasses (BMG). First, we will show how NMR can be used to detect ultraslow atomic motions. This study demonstrates that atomic diffusion in such BMG systems proceeds via two parallel processes, single-atom hopping and collective motions of groups of atoms. The former dominates below the glass transition temperature T_g whereas the latter dominates above T_g. Second, we will show how NMR can be used to detect the root-mean-square atomic displacement caused by vibrations over the entire temperature range up to above the liquidus temperature in BMG systems. A rapid transition of versus T was observed above T_g in Pd-based BMGs. The relationship of this transition to mode-coupling theory and neutron scattering data will be discussed. Finally, we will show how NMR can be used to probe structural information in metallic glasses.