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Faraday rotation and superconducting quantum interference device magnetometry were used to investigate the relaxation of the weak-field induced remanence, µ, of the random-field Ising model system Fe1-xZnxF2. The stretched logarithmic decay law, as predicted by Nattermann and Vilfan for the case of compact domains with fractal surfaces, was confirmed for freezing fields of 3≤B≤5 T. Virtually constant remanence, µ, was found at low fields, 0.0002≤B≤1.5 T. This ferrimagnetic moment is due to the piezomagnetic effect acting on random-stress induced immobile domains. Chemical etching, which removes surface stress originating from the sample preparation, proves to decrease the remanence by about 50%, part of which is restored after renewed optical polishing. Journal of Applied Physics is copyrighted by The American Institute of Physics.