Non-collinear magnetic order in a Sc-substituted barium hexaferrite

A combined magnetic, neutron diffraction and field-dependent Fe-57 Mossbauer study of Sc-substituted Ba-hexaferrite in powder form is reported, and the findings are compared with the data for BaFe12O19. The five cation sublattice with collinear ferrimagnetic structure of uniaxial (Gorter) type for BaFe12O19, persists also for BaFe10.4Sc1.6O19 at room temperature and below down to 130-190 K, depending on the applied field. Below room temperature, BaFe10.4Sc1.6O19 undergoes a magnetic transition as indicated by the magnetization and Mossbauer spectroscopic measurements. The neutron diffraction results are compatible with a gradual transformation below 190 K into a complex canted structure with spins pointing out of the axial direction. The complex magnetic order at 10 K can be described in terms of an incommensurate complex block-type conical structure. (C) 2006 Elsevier B. V. All rights reserved.