Synthesis and magnetic properties of La-substituted M-type Sr hexaferrites

Single-phase M-type hexagonal ferrites Sr1-xLaxFe12O19 (0 <= x <= 1) were prepared by a ceramic route. The stability limits of the ferrite phases were determined with a combination of various microscopy techniques, electron-probemicro-analysis, powder X-ray diffraction and thermal analysis. SrFe12O19 ( x = 0) is stable up to 1420 degrees C, whereas LaFe12O19 (x = 1) exists between 1360 and 1400 degrees C only. The lattice parameters of Sr1-xLaxFe12O19 exhibit a linear variation with x, i.e. a(0) slightly increases and c(0) decreases with x, leading to a decrease of the unit cell volume with x. The saturation magnetization at T = 5KdecreaseswithincreasingLaconcentration. Room temperature Mossbauer analysis shows that the Fe3+/Fe2+ valence change occurs in the 2a sites for the whole composition range. (C) 2009 Elsevier B.V. All rights reserved.