Fe/Sr ratio effect on magnetic properties of strontium ferrite powders synthesized by microwave-induced combustion process

Strontium hexaferrite nano-particles were successfully synthesized by microwave-induced combustion process. Magnetic properties of strontium ferrite powders with Fe/Sr ratios varying from 11 to 12 and different annealing temperatures range of 850 to 1050 °C were studied. The resultant powders were investigated by XRD, TEM, SEM, VSM, TG/DTA, and surface area measurement. The optimum magnetic properties of strontium ferrite powders were as follows: the composition with an Fe/Sr ratio of 11.6 annealed at 1000 °C for 2 h possessed a saturation magnetization of 62 emu/g and an intrinsic coercive force of 1950 Oe. Moreover, the microwave-heated strontium ferrite powders with a Fe/Sr ratio of 11.6 annealed at various temperatures had particle size ranging from 52 to 78 nm. Low-coercivity strontium ferrite powders can be obtained by microwave-induced combustion process without doping with metal elements such as Co-Ti, Co-Sn, Zn-Sn, etc. These low coercive strontium ferrite powders are suitable for magnetic recording applications in hard disks, floppy disks, video tapes, etc.