An investigation of the spin glass behaviour in iron antimonate by iron-57 and antimony-121 Mössbauer spectroscopy

Iron antimonate, which contains a superlattice composed of an ordered array of cations in the rutile-type structure, has been shown to undergo a spin glass transition atca. 20K which is induced by antisite atomic ordering. The iron-57 Mössbauer spectra recorded at 298 and 77K provide information on the relaxation times of short range magnetically ordered clusters identified by magnetic susceptibility measurements. The spectrum of 4K is tentatively interpreted in terms of the existence, at temperatures below the spin glass transition temperature, of a hyperfine magnetic field distribution at Fe³⁺ ions with a mean value of 487 kOe and which contains a supertransferred contribution from the nearest neighbour Fe³⁺ ions. The¹²¹Sb Mössbauer spectra are characteristic of Sb⁵⁺ and the increasing linewidths at lower temperatures are consistent with the presence of a supertransferred hyperfine magnetic field at the Sb⁵⁺ species ofca. 16^kOe.