Critical scaling of the EPR linewidth in the Ag-Mn spin glass

We have measured the EPR linewidth and shift between 1 and 10 GHz in the paramagnetic regime of the Ag-Mn(2.6 at. %) spin glass. The critical part of the linewidth can be described equally well within experimental error either by dynamic (frequency) scaling, $W^{\mathrm{ex}}$∝$t^{\mathrm{-}g}$G(ω/$t^{\nu z}$), or by field scaling, $W^{\mathrm{ex}}$∝$t^{\mathrm{-}g}$G(H/$t^{(\beta +{\gamma }_s)/2\mathrm{}}$ ). The experiments give g=1.5 and either νz=2.5 or (β+${\gamma }_s$)/2=2.5. The adequacy of the scaling form is taken as evidence favoring a thermodynamic phase transition of the usual type at $T_g$. Within experimental error, $T_g$ is independent of applied magnetic field, and within the Sherrington-Kirkpatrick model, $T_g$ may be identified with the Gabay-Toulouse line for transverse freezing.