Production and Magnetic Properties of Co- and La-Y-Doped Strontium Ferrite

In this study, rare earth-substituted M-type Sr-hexaferrites with the chemical compositions Sr1-x(RE)(x)Fe12-xCoxO19 and Sr1-2x(RE)(2x)Fe12-xCoxO19 were prepared using the solid-state reaction method. All of the hexaferrite samples were characterized using instrumental techniques of X-ray diffraction, optical microscopy, and vibrating sample magnetometer to study the effect of La-Y substitution on the structural and magnetic properties. The bulk densities changed from 4.45 to 4.96 g/cm(3) after sintering at 1250 degrees C. X-ray diffraction diagrams of all the sintered samples confirmed that the Sr-hexaferrite phase persisted with La/Y and Co co-substitution without secondary phases. However, the substitution affected the peak intensities and the positions of Bragg angles. The reduction in the saturation magnetization (M-s) was observed from 25.4 emu/g for single La to 9.40 emu/g for La-Y substitution. It was found that the coercivity (H-c) improved from 502 to 2080 Oe for a single Y-substituted sample and a single La-substituted sample, respectively. The measured squareness ratio (M-r/M-s) was larger than 0.5, indicating that the change in the magnetization can be realized by the rotation. The results suggest that the incorporation of rare-earth cations can improve the magnetic properties of strontium hexaferrites.