Low-field dc-magnetization and thermoremanent-magnetization measurements have been recorded from the rutile-related iron antimonate of composition FeSbO 4 . The zero-field-cooled susceptibility curve at low magnetic fields (H=20 Oe) shows a small peak at ∼72 K and a much broader peak at lower temperatures of ∼25 K. The temperature dependence of the remanent magnetization below ∼72 K indicates the existence of two different relaxation regimes which depend on the strength of the applied field in which the sample was cooled. The thermoremanent-magnetization measurements as a function of time show aging effects and the characteristic parameters are quite similar to those found in canonical spin glasses. The temperature dependence of the first nonlinear coefficient b 3 in the expansion of the magnetization in odd powers of ( a 1 H) shows no divergence around the peak at 72 K, which is indicative of the absence of a true spin-glass transition. The moderate degree of frustation associated with an inhibited antiferromagnetic transition at ∼72 K, is nevertheless insufficient to produce a true spin-glass transition where the magnetic correlation length is even much shorter.