'Publishing House for Science and Technology, Vietnam Academy of Science and Technology'
Abstract
Two series of SrFe12O19/NiFe2O4 nanocomposite ferrites sintered in air at 850\rc{}C and 950\rc{}C were prepared using SrFe12O19 and NiFe2O4 nanopowders obtained via sol-gel method. The phase composition, surface morphology and magnetic properties of the composites were investigated using XRD, SEM and VSM respectively. For the SrFe12O19/NiFe2O4 ferrites with volume ratio ranging from 61 to 21 and sintered in 850˚C for 5 hours in air, all the specimens are composed of two phases but exhibit a typical single-phase magnetic behavior, indicating the existence of exchange coupling (EC) between the magnetically hard and soft phases. The value of coercivity Hc decreases from 6.19 kOe to 0.574 kOe when volume of SrFe12O19 decreases from 6 to 1. While the samples with a mass ratio of Rm= SrFe12O19/ NiFe2O4 varying from 31 to 13 sintered in 950\rc{}C for 5 hours characterized with a ``bee waist'' type hysteresis loop. These results reveal that the magnetically hard and soft magnetic phases are not exchange- coupled. The saturation magnetization (MS) increases from 36 emu/g to 43.3 emu/g when Rm decreases from 31 to 13 and then decreases with Rm=12 and 13