Effects of Annealing Temperature on Exchange Spring Behavior of Barium Hexaferrite/Nickel Zinc Ferrite Nanocomposites

(BaFe12O19)(1-x) /(Ni0.6Zn0.4Fe2O4) (x) magnetic nanocomposites with various molar ratios (x = 0.0, 0.1, 0.2, 0.3) have been synthesized by a physical mixing method at different temperatures (T = 700A degrees C to 900A degrees C) and their structure, morphology, and magnetic properties investigated using x-ray diffraction analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and vibrating-sample magnetometry. The results prove that their magnetic properties were strongly influenced by the sintering temperature as well as the molar ratio of hard to soft phase. The magnetization and switching field distribution curves for the nanocomposites sintered above 800A degrees C showed a single smooth hysteresis loop, suggesting the existence of the exchange spring phenomenon. The variation of the coercivity, saturation magnetization, and ratio of remanence to saturation magnetization (M (r)/M (s)) with the hard-to-soft weight ratio can be explained based on the role of exchange and dipole interactions in the nanocomposites. High maximum energy product (BH)(max) was obtained for the (BaFe12O19)(0.9)/(Ni0.6Zn0.4Fe2O4)(0.1) sample annealed at 800A degrees C.