Static and dynamic critical phenomena inFe1−xZnxF2

The critical behavior of the diluted Ising antiferromagnet $\mathrm{F}{\mathrm{e}}_{1-x}{\mathrm{Zn}}_x{\mathrm{F}}_2$ has been studied by Mössbauer spectroscopy. The value of the magnetization critical exponent is observed to cross over abruptly from the pure Ising $\beta =0.33\mathrm{}$ to the predicted random-exchange Ising $\beta =0.36\mathrm{}$. This crossover occurs in the reduced temperature range $t={10}^{-1\mathrm{}} \mathrm{to} {10}^{-3\mathrm{}}$ at dilutions $x<\mathrm{}0.07\mathrm{}$. The critical dynamics was measured above and below $T_N$ and crossover from a pure Ising to a random-exchange Ising behavior as a function of $x$ was observed with increasing dilution.