Nuclear Magnetic Resonance in Random Fields: Cluster Formation and Local Dynamics of a Deuteron Glass

Abstract

NMR data show that the deuteron "pseudo spin-glass" transition in ${\mathrm{Rb}}_{1\ensuremath{-}x}{(\mathrm{N}{\mathrm{D}}_{4})}_{x}{\mathrm{D}}_{2}\mathrm{P}{\mathrm{O}}_{4}$ is not just a simple kinetic slowing down process but is characterized by a gradual condensation of randomly polarized clusters as expected if we deal with a percolation transition in eigenstate space. The results provide novel information on the temperature dependence and distribution of local random fields and their dynamics. The spin-lattice and motional-narrowing data further suggest that the "pseudospin" O---D--O deuteron intrabond motion determines the freezing dynamics.