Influence of the cation distribution on the magnetization of Y-type hexagonal ferrites

Mössbauer absorption and magnetization measurements have been made in Mg₂?Y and Co₂?Y ferrites. The magnetizations of the various iron sublattices did not show any marked difference in Mg₂?Y, whilst in the case of Co₂?Y three different behaviours of the sublattice magnetizations have been detected. Low-temperature magnetization measurements in Mg₂Y gave evidence of a noncollinear magnetic order. The different magnetic properties of these compounds have been explained on the ground of a preferential occupation by Mg²⁺ and Co²⁺ ions of the inner octahedral sites of the T crystallographic block. The presence in these sites of a non-magnetic ion such as Mg²⁺ is responsible for the peculiar magnetic order observed in Mg₂?Y.