Magnetic properties of Co and Ti co-doped strontium hexaferrite prepared by sol–gel method

The Co and Ti co-doped SrFe12O19 hexaferrites have been successfully synthesized via the sol–gel method. The X-ray diffraction patterns demonstrate that all doped samples are single-phase hexagonal crystal confirmed by Rietveld refinement. The results of field-emission scanning electronic microscopy reveal that the particle sizes increase obviously with increasing Co–Ti substitution rate. It can be clearly observed that the magnetic properties can be effectively tuned by the partial substitution of Fe with Co and Ti. The magnetization measurement manifests both saturation magnetization and coercivity drop with increasing Co–Ti concentration. Specifically, the coercivity falls substantially from about 1697 to 20 Oe with only a little decrease in the saturation magnetization as x increases from 0.5 to 1.5. The results indicate that low-doped Co–Ti substitution rates (x) make hexaferrites suitable for high density and perpendicular recording technology. It is worthy to note that the Co–Ti substituted samples can gradually turn the magnetocrystalline anisotropy from uniaxial to planar, and the transition point is near x = 1.5, which is beneficial to the formation of a conical magnetic structure to induce electric polarization. It is expected that Co–Ti co-doped hexaferrite Sr(CoTi)1.5Fe9O19 may be potential candidates for application based on the magnetoelectric devices.