Cation distribution and random spin canting in LaZnFe11O19

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Abstract
A new M-type hexagonal ferrite with composition LaZnFe11O19 has been synthesised and its cation distribution and magnetic properties have been investigated. The location of Zn ions among the five sublattices of the M structure has been deduced from temperature dependent Mossbauer spectra. It is found that less than 10% of Zn ions may occupy the pseudo-tetrahedral 4e sublattice, the remaining Zn ions being located at the tetrahedral 4fIV sublattice. From both, the low value of the saturation magnetisation, M0=19.0 mu BFU-1, and the observation of a high field differential susceptibility it is concluded that LaZnFe11O19 has a non-collinear magnetic structure. Based on the hyperfine interactions and cation distribution obtained from the Mossbauer spectra the authors propose the existence of a random spin canting in the octahedral 12k and 2a sublattices. A theoretical analysis in the scope of the random spin canting model is performed in order to justify the observed noncollinear disordered spin structure.