Morphological and magnetic characteristics of strontium ferrite micro- and nanofibers

Strontium ferrite micro- and nanofibers have been prepared by the sol-gel process and the electrospinning with diameters about 1 mu m and 100 nm, respectively. Single phase strontium ferrite fibers are formed after calcined at 750 degrees C for 2 hours for both the sol-gel and electrospinning processes. These strontium ferrite fibers are fabricated of nanosized particles with a hexagonal plate-like morphology, which grow with the calcination temperature. The microfiber cross-section contains multi-nanoparticles whilst the nanofiber with a necklace-like morphology is linked by nanoparticles at the calcination temperature range from 850 to 1050 degrees C. The magnetic properties of strontium ferrite fibers are mainly influenced by the grain size and fiber diameter. Both the strontium ferrite micro- and nanofibers calcined at 900 degrees C for 2 hours are fabricated from single-domain grains around 56 nm and exhibit the specific saturation magnetization of 60.8 A.m(2).kg(-1) (microfibers) and 59.9 A.m(2).kg(-1) (nanofibers) and coercivity of 361.9 kA.m(-1) (micronfibers) and 523.6 kA.m(-1) (nanofibers). The coercivity difference between the micro- and nanofibers can be attributed to the different shape anisotropy energies arising from various magnetization reversal behaviors for the micro- and nanofibers.