Mn-doped (Ba, Y)Fe12O19 hexaferrites: Crystal structure and oxidation states of Mn and Fe

Abstract We have fabricated Ba0.95Y0.05Fe12-xMnxO19 samples with large Mn-doping amounts of x = 4 and 6, using the mechanical milling and heat treatment. X-ray diffraction analysis indicated the samples crystallized in the M-type hexaferrite structure. The Mn doping caused the modification, shift and broadening of some characteristic phonon-vibration modes, which were recorded by Raman spectroscopy. This is due to an incorporation of Mn ions into the M-type structure that disorders the periodic lattice and changes symmetry. Basing on X-ray absorption spectroscopy, we have found Fe in all samples stable with an oxidation state 3+ (Fe3+). Though Mn2+ and Mn3+ ions coexist, the concentration of Mn2+ in x = 4 is larger than that in x = 6. The analysis of Fourier-transform spectra have demonstrated the replacement of Mn2+,3+ ions for Fe3+ in the M-type structure. The sites of Mn2+,3+ ions in this structure have been discussed.