Ba0.5Sr0.5Fe12O19(hard)-CoFe2O4(soft) nanocomposite ferrites synthesized using the citrate-gel combustion method was subjected to different annealing temperatures (Ta) (700 °C, 800 °C, 900 °C, and 1000 °C), and the resultant structural and magnetic properties were investigated. The microstructural characterization of nanocomposites via X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) analysis at first revealed the dominance of soft phases annealed at 700 °C and then showed the presence of hard phases at 900 °C. Lattice vibrational analysis again showed a clear distinction between the bands corresponding to Ta at 700 °C and 900 °C. An increase in saturation magnetization (MS) and coercivity (HC) was observed upon increasing the Ta. A good combination of MS (56.9 emu/g) and HC (3.3 kOe) was obtained at Ta = 900 °C. In addition, high-temperature magnetic studies confirmed the dominance of soft phase with Curie temperatures of 592 °C and 480 °C for the samples annealed at 700 °C and 900 °C, respectively. Combining these facts, a detailed mechanism involving the domination of spinel plates and hexagonal layers was drawn. The magneto crystalline anisotropy was evaluated and showed a maximum for Ta at 900 °C. The extent of exchange coupling between the hard and soft phases was further analyzed by switching field distribution curves and is discussed in detail. © 2018 Elsevier Ltd