Mossbauer spectroscopic determination of magnetic moments of Fe3+ and Co2+ in substituted barium hexaferrite, Ba(Co,Ti)xFe(12-2x)O19

We report the distribution of magnetic moments of Fe3+ and Co2+ in Co2+, Ti4+-substituted M-type barium hexaferrite, Ba(Co,Ti)(x)Fe(12-2x)O19, as a function of doping rate, x. The substitution, x, for iron has been varied with x = 0, 0.25. 0.50, 0.70 and 0.85. The magnetic moments of Fe3+ and Co2+ were calculated from the combined results of Mossbauer measurements for Fe3+ ions in the sublattices and neutron diffraction data for the total moments of Fe3+ and Co2+. A comparison of the signs of the magnetic moments of Fe3+ and Co2+ ions enabled us to attribute spin directions of the Co2+ ions in the sublattices of the substituted ferrite samples. The spin directions of Co2+ are opposite to those of Fe3+ in the 4f(2) and 2b sublattices. They are reversed from the original directions in the 4f(1) and 12K sublattices when the value of x greater than or equal to 0.70. A quantitative analysis shows that Co2+ and Ti4+ ions are preferably substituted into 4f(2) and 12K sublattices, respectively. In addition, while the hyperfine field of Fe3+ in the 2b sublattice gives rise to the 2b-4f(2) interaction it is the partially substituted Co2+ ions in the 4f(1) and 12K sublattices that contribute to the near neighbour 2a-4f(1) and 2b-12K types of interaction. (C) 2000 Elsevier Science B.V. All rights reserved.