Cation distribution and magnetic structure of M-type BaTiMnFe₁₀O₁₉ examined by synchrotron X-ray and neutron studies

Combinational studies of synchrotron X-rays and neutrons have been performed to determine the site occupancy, valence state and magnetic structure of M-type BaTiMnFe₁₀O₁₉. X-ray resonant scattering studies have revealed the site preference, where Ti and Mn ions are distributed evenly over the Fe1, Fe2 and Fe3 sites of five independent Fe sites. X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) results for BaTiMnFe₁₀O₁₉ are similar to those of BaFe₁₂O₁₉ at the Fe K absorption edge. Clear chemical shifts exist at both the Mn and Fe edges, suggestive of a mixed valence of Mn and Fe ions. The Mn K XANES resembles Mn–Zn ferrite, where the observed fourfold peak is explained as the presence of four-coordinated Mn ions, on the basis of the self-consistent calculation of relativistic density functional theory. This can be explained by the presence of spinel substructures within the S block layer. Satellite reflections of 002 ± τ and 004 − τ (τ = 2/3) on 00l were observed at a temperature of 8 K in neutron powder diffraction, due to magnetic scattering on the helicoidal arrangement of ordered spins with a propagation period of c/τ. The magnetic structure observed in the neutron powder diffraction and the XMCD results explain the decreasing uniaxial magnetization from BaFe₁₂O₁₉.