Barium ferrite prepared by chemical coprecipitation has been investigated with microwave and static magnetization measurements. The resonance absorption in negative field, predicted by the single domain theory, has been found. The coercive force JHc and the saturation magnetization σs can be improved with acid treatment, values of JHc = 6 400 Oe and σs = 70.7 emu/g are obtained. Both conventional sintering and rapid hot-pressing lead to a high density and good magnetic properties. A density of ρ = 5.02 g/cm3 and a maximum energy product of (BH)max = 1.4 MGOe were achieved by rapid hot-pressing