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Structural and Mössbauer analyses of ultrafine Sr 1 x La x Fe 12 x Zn x O 19 and Sr 1 x La x Fe 12 x Co x O 19 hexagonal ferrites synthesized by chemical co-precipitation

2004; IOP Publishing; Volume: 16; Issue: 29 Linguagem: Inglês

10.1088/0953-8984/16/29/025

1361-648X

L. Lechevallier, J.M. Le Breton, J F Wang, I.R. Harris,

Multiferroics and related materials

Ultrafine M-type hexagonal ferrites of nominal composition Sr1−xLaxFe12−x ZnxO19 and Sr1−xLaxFe12−xCoxO19 with x = 0, 0.1, 0.2, 0.3 and 0.4 were produced by chemical co-precipitation. The phase make-up of the samples was investigated by x-ray diffraction. The analyses show that the hexagonal M-type phase is the main phase in all the samples. Secondary (La,Sr)FeO3, ZnFe2O4 and CoFe2O4 phases are also detected, indicating that the La, Zn and Co content in the M-type phase is lower than the nominal content. A complete Mossbauer analysis of the substitution effects in the M-type phase was made. The results show that the M-type phase contains La3+ in the same proportion as Zn2+ and La3+ in the same proportion as Co2+, in the La–Zn and La–Co samples, respectively. The evolution with x of the hyperfine parameters of the components used to fit the contribution of the M-type phase have been interpreted consistently in relation to the substitution effects by means of the comparison between the spectra of the La–Zn and La–Co substituted samples. The results show unambiguously that La3+ ions are located in the Sr2+ sites, Zn2+ ions are located in the 4f1 sites and Co2+ ions are located in both 4f2 and 2a sites.