Fabrication of M-type ferrites with high La-Co concentration through Ca 2+ doping

Abstract Ca 2+ doped Sr 0.45- x Ca x La 0.55 Fe 11.6 Co 0.4 O 19 ( x  = 0, 0.15, 0.3, and 0.45) ferrites were fabricated through a conventional ceramic process. The influences of Ca 2+ doping on the microstructure and magnetic properties of ferrites were investigated. Ca 2+ doping could mitigate the presence of impurity phase (CoFe 2 O 4 ) in ferrites. Single phase M-type ferrites could be fabricated when x  ≥ 0.3. Additional Co 2+ ions entered the crystal lattice and preferentially occupied the 4f 2 site with Ca 2+ doping. This effect greatly improved the remanence (B r ) and intrinsic coercivity (H cj ) when x increased from 0 to 0.3. The average grain size of sintered ferrites slightly increased with the amount of doped Ca 2+ ions. This behavior led to the deterioration of H cj when x increased from 0.3 to 0.45. Consequently, ferrite prepared with x  = 0.3 presented the highest maximum energy product ((BH) max ) of 5.24MGOe. This performance is much higher than that of conventional La-Co substituted Sr-ferrites.