Cation distribution and valence state in Mn-Zn ferrite examined by synchrotron X-rays

摘要

Cation distribution and valence state in manganese zinc ferrite have been investigated with the synchrotron X-rays, where the two-wavelengths anomalous dispersion (TWAD) technique of X-ray diffraction was used at wavelengths of 1.7535 and 1.2934 angstrom for Fe K and Zn K absorption edges, respectively. The result shows that a single crystal of Mn0.80Zn0.18Fe2.02O4 grown at T = 1373 K has an inverse-spinel ingredient, where 11% of Mn and 44% of Zn ions occupy the octahedral B sites of spinel ferrite. The cation distribution is quite different from that of manganese zinc ferrite manufactured, which was synthesized at T = 1873 K and has a typical normal-spinel structure. The chemical shifts in Mn K, Zn K and Fe K X-ray absorption near-edge structure (XANES) spectra support that only Mn2+, Zn2+ and Fe3+ ions exist in the manganese zinc ferrite. From a combination study of XANES and X-ray magnetic circular dichroism (XMCD) spectroscopy at the Mn K edge, it is suggested that Mn2+ ions occupy both tetrahedral A and octahedral B sites. The chemical formula determined in this study is described as (Mn-0.71(2+) Zn-0.10(2+) Fe-0.19(3+)) [Mn-0.09(2+) Zn-0.08(2+) Fe-1.83(3+)]O-4.