NONCRITICAL BEHAVIOR AND REMANENT MAGNETIZATION IN MAGNETICALLY FRUSTRATED FESBO4

Low-field dc-magnetization and thermoremanent-magnetization measurements have been recorded from the rutile-related iron antimonate of composition FeSbO4. The zero-field-cooled susceptibility curve at low magnetic fields (H = 20 Oe) shows a small peak at approximately 72 K and a much broader peak at lower temperatures of approximately 25 K. The temperature dependence of the remanent magnetization below approximately 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 b3 in the expansion of the magnetization in odd powers of (a1H) 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 frustration associated with an inhibited antiferromagnetic transition at approximately 72 K, is nevertheless insufficient to produce a true spin-glass transition where the magnetic correlation length is even much shorter.