High-frequency dynamics and the spin-glass transition

We identify two distinct regimes in the high-frequency response of the insulating, Ising spin-glass, $\rm LiHo_{0.167}Y_{0.833}F_4$. The asymptotic high-frequency behavior of the imaginary part of the magnetic susceptibility becomes frequency independent as the spin-glass transition is approached: the shortest and the longest measured time scales both contain information about the actual phase transition. We compare our results to corresponding data on supercooled liquids.