Relaxation of the excess magnetization of random-field-induced metastable domains in ${\mathrm{Fe}}_{0.47}$${\mathrm{Zn}}_{0.53}$${\mathrm{F}}_2$

The Faraday rotation of the excess magnetization in the field-cooled random-field Ising antiferromagnet ${\mathrm{Fe}}_{0.47}$ ${\mathrm{Zn}}_{0.53}$ ${\mathrm{F}}_2$ has been measured for fields 0<H<7 T applied along the easy axis at temperatures 5 K<T<22 K, well below the H=0 phase transition occurring at T=${\mathit{T}}_{\mathit{N}}$ (=37 K). The relaxation of the excess magnetization, which is proportional to the Faraday rotation, does not follow the Nattermann-Vilfan theory in detail for this range of T and H. We explore other possible forms for the time dependence of the excess magnetization and use Monte Carlo techniques as an aid in the interpretation of the experimental data.