Structural analysis of hydrothermally synthesized Sr1-xSmxFe12O19 hexagonal ferrites

M-type hexagonal ferrites of composition Sr1-xSmxFe12O19 with x = 0, 0.06, 0.11, 0.2 and 0.33 were produced by hydrothermal synthesis. The purity of the samples was investigated by X-ray diffraction and Mossbauer spectrometry. The analyses reveal for all the samples the presence of the hexagonal M-type phase as the main phase, but also the presence of Sm containing secondary phases of the (Sr,Sm)FeO3-delta type. The results of the Mossbauer analysis show that the hyperfine parameters of the M-type phase contribution do not vary with the Sm content, indicating that the Sm content in the M-type phase is very weak. This is in agreement with the fact that no Fe 21 is detected in the spectra. As both anisotropy field and saturation magnetization remain constant, the increase of the coercivity is thus attributed to microstructural changes, in relation with the presence of the Sin containing secondary phases. (C) 2003 Elsevier B.V. All rights reserved.