Dynamics of the spin-glass freezing in semimagnetic semiconductors

Accurate measurements of the imaginary part of the complex susceptibility are used in order to compare the validity of different dynamic scaling models on the two related spin-glass compounds ${\mathrm{Hg}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te and ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te (x=0.3). The conventional power-law scaling yields in both compounds a dynamic exponent zν=9±1, $T_c$=8.4 K for ${\mathrm{Hg}}_{0.7}$ ${\mathrm{Mn}}_{0.3}$Te and 6.45 K for ${\mathrm{Cd}}_{0.7}$ ${\mathrm{Mn}}_{0.3}$Te. The generalized in-field scaling leads to an independent and consistent determination of $T_c$. Good scalings may also be achieved according to activated dynamics, but the P values appear to differ in various systems, a result at odds with the expected universality of the critical exponents.