Improved magnetic properties of SrFe12O19/FeCo core–shell nanofibers by hard/soft magnetic exchange–coupling effect

●SrFe12O19/FeCo core–shell nanofibers were fabricated by coaxial electrospinning and reduction process.●Magnetic properties of SrFe12O19/FeCo core–shell nanofibers are improved by the hard/soft exchange–coupling effect.●The saturation magnetization for SrFe12O19/FeCo core–shell nanofibers increases to 68.8 emu/g comparing with SrFe12O19 nanofibers (53.4 emu/g).

Hard/soft SrFe12O19/FeCo composite nanofibers with core–shell structure have been synthesized by reduction process in a hydrogen atmosphere. As the precursor, SrFe12O19/CoFe2O4 core–shell nanofibers were prepared by coaxial electrospinning and calcination process. SrFe12O19/CoFe2O4 composite ferrites were formed after calcined at 900 °C for 1 h. The core–shell nanofibers show an enhanced saturation magnetization (Ms) of 60.9 emu/g for SrFe12O19/CoFe2O4 and 68.8 emu/g for SrFe12O19/FeCo comparing with SrFe12O19 nanofibers (53.4 emu/g). The coercivities (Hc) for SrFe12O19/CoFe2O4 and SrFe12O19/FeCo core–shell nanofibers decrease to 3190 Oe and 1249 Oe, respectively. The hysteresis loop for SrFe12O19/FeCo core–shell nanofibers shows a single-phase magnetization behavior. The improvement in magnetic properties for core–shell structure composite nanofibers is attributed to the exchange–coupling interaction between the hard and soft phases.