Structural and magnetic properties of hydrothermally synthesised Sr1-xNdxFe12O19 hexagonal ferrites

M-type hexagonal ferrites of composition Sr1-xNdxFe12O19 with x = 0, 0.06, 0.08, 0.11, and 0.20 were produced by hydrothermal synthesis. The phase composition 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. However, Nd containing secondary phases of the (Sr,Nd)FeO3-delta type are also detected. Mossbauer spectrometry indicates that the Nd content in the M-type phase is very weak, as the hyperfine parameters of the M-type phase contribution do not vary with the Nd content. This is in agreement with the fact that both saturation magnetisation and remanence remain almost constant as the Nd content increases. The variations of the coercive field are thus attributed to microstructural changes, in relation with the presence of the Nd containing secondary phases. (C) 2003 Elsevier B.V. All rights reserved.