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Effects of Li2CO3 addition on structural and magnetic properties of M-type strontium hexaferrite have been studied by using crystallographic and magnetic measurements. The samples were prepared thru the flux-aided solid state reaction by adding small fractions of Li2CO3 powder to the SrFe12O19 precursors. The key action of a flux salt is strongly dependent upon solubility and dispersion of the salt ions over the grain. So, the crystallographic, microstructural, and macroscopic magnetic characteristics have been explored in relations with the role of flux salt by means of XRD, FE-SEM, VSM, and Mössbauer spectroscopy. Finally, the result strongly suggests that most of the flux salt Li1+ ions distribute throughout the grain surface and act like a surfactant that enhance the degree of grain separation and thereby reduce the coercivity of the sample.

Effects of stoichiometric La3+–Li1+ co-substitution on magnetic properties of M-type strontium hexaferrites Sr1-xLaxFe12-x/2Lix/2O19 (x = 0, 0.25, 0.4, 0.5, 0.6) have been studied by using crystallographic and magnetic measurements. Samples were prepared thru conventional ceramic technique and their powder X-ray diffraction profiles were checked by the Rietveld method using GSAS package. Field emission scanning electron microscopy images show that lithium addition derives the enhanced degree of grain separation, which significantly affects the coercivity and anisotropy constant as examined by vibrating sample magnetometer measurement. 57Fe Mössbauer spectra of the samples show that Li1+ ions preferentially occupy the 2a sites, which causes the decrease of MS with lithium addition.

Effects of La3+ and Cu1+ co-doping on the structural and the magnetic properties of M-type strontium hexaferrite have been studied by using crystallographic and magnetic measurements. Stoichiometric samples have been prepared by a conventional ceramic technique with repeated sintering at 1300 °C for 24 hours in the air. XPS Cu 2p scan shows that dominant valence state of Cu is +1. Analyses of the hysteresis curve reveals that MS increases and HC decreases with La-Cu content x. Room temperature Mössbauer spectral analysis indicates that Cu1+ preferentially replaces Fe3+ at 4f2 site, which is consistent with the increase of MS with respect to the La3+-Cu1+ co-doping.

Effects of nonmagnetic indium ion substitution on magnetic properties of M-type strontium hexaferrites SrFe12-xInxO19 (x=0, 0.25, 0.5, 0.75, and 1) have been studied by crystallographic and magnetic measurements. Samples were prepared by citric auto-combustion method. Rietveld analysis of X-ray diffraction profiles showed that the samples were single phase with the space group P63/mmc and lattice constants a and c increased linearly with In3+ content. Mössbauer spectra showed that In3+ mainly replaced Fe3+ ions in 4f2 sites and that 12k subspectra split into two distinct components 12k1 and 12k2. Analysis of hysteresis curves showed that while the coercive force and the magnetic anisotropy constant decreased thru the whole doping range x, the saturation magnetization first increased until x=0.5 and decreased thereafter. This behavior was explained by the existence of two competing interactions in terms of nonmagnetic indium substitution.