Effects of Gd substitution on the structural and magnetic properties of strontium hexaferrites

The effect of Gd substitution in M-type strontium hexaferrites has been examined in two series of samples, (Sr1-xGdx)O·5.25(Sr1-xGdx)O·5.25Fe2O3Fe2O3 and Sr1-xGdxFe12-xCoxO19Sr1-xGdxFe12-xCoxO19, both prepared by the ceramic method, where x=0–0.40x=0–0.40. The samples have been characterized by XRD, VSM and SEM-EDAX techniques. All substituted samples present primarily the hexaferrite structure. Sample (Sr0.95Gdx0.05)O·5.25(Sr0.95Gdx0.05)O·5.25Fe2O3Fe2O3 is single phase. Formation of impurity phases is affected by stoichiometry and presence of Co. In Sr–Gd samples, coercivity showed a maximum value of 305 kA/m (3.8 kOe) for x=0.20x=0.20, while remanence and saturation magnetization did not decrease. Coercivity and magnetization in the Sr–Gd–Co series decreased steadily with substitution degree.