Magnetic properties and spin order of Sr7Fe10O22

The magnetic properties of Sr7Fe10O22 have been investigated by means of magnetic susceptibility and Mossbauer absorption measurements. This compound proved to be antiferromagnetic with a Neel temperature TN = 425 K; the magnetic susceptibility is constant from the lowest measuring temperature (78 K) up to TN. The Mossbauer measurements and the analogies with “brownmillerite” type compounds indicate that iron ions occupy one octahedral and two tetrahedral different sites. An antiferromagnetic spin configuration with moments lying in the ab plane appears to be consistent with the experimental results. A small spontaneous magnetic moment was observed at room temperature with features resembling those of strontium hexaferrite; a weak ferromagnetic behavior can not however be excluded taking into account the aforementioned susceptibility behaviour.