Ordering and relaxation in spin glasses

Ordering and relaxation in spin glasses are discussed in terms of the diffusion of the point representing the system in eigenstate space. On this approach, the spin-glass transition $T_g$ appears as a percolation threshold; stretched exponential relaxation behavior extends from $T_g$ to an upper characteristic temperature $T_c$. Predictions are consistent with three-dimensional Ising simulations by Ogielski. Experimental data suggest that for real metallic spin glasses $T_c$≃1.5$T_g$. This approach may be relevant for other broad-spectrum relaxation phenomena.