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 degrees C for 1 h. The core-shell nanofibers show an enhanced saturation magnetization (M-s) 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 (H-c) 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. (C) 2014 Elsevier B.V. All rights reserved.