Static and dynamic critical phenomena in F e 1 − x Zn x F 2

The critical behavior of the diluted Ising antiferromagnet $\mathrm{F}{\mathrm{e}}_{1\ensuremath{-}x}{\mathrm{Zn}}_{x}{\mathrm{F}}_{2}$ has been studied by M\"ossbauer spectroscopy. The value of the magnetization critical exponent is observed to cross over abruptly from the pure Ising $\ensuremath{\beta}=0.33$ to the predicted random-exchange Ising $\ensuremath{\beta}=0.36$. This crossover occurs in the reduced temperature range $t={10}^{\ensuremath{-}1} \mathrm{to} {10}^{\ensuremath{-}3}$ at dilutions $xl0.07$. 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.