Stretched-exponential nuclear magnetization recovery in the proton pseudo-spin-glass Rb1−x(NH4)xH2AsO4

Abstract

The proton spin-lattice recovery function at high magnetic fields and the nuclear magnetization decay in the rotating frame are nonexponential in the incipient proton glass ${\mathrm{Rb}}_{1\mathrm{-}\mathrm{x}}$(${\mathrm{NH}}_4$ ${)}_{\mathrm{x}}$ ${\mathrm{H}}_2$ ${\mathrm{AsO}}_4$. The results can be described by a stretched-exponential correlation and magnetization-recovery function with the distribution parameter n in α=1-n varying from zero at room temperature to 0.25 at 100 K and 0.4 at temperatures below 12 K. The same values of n are obtained at high magnetic fields and in the rotating frame.