Synthesis of a novel rare earth free Co3C-Co0.35Fe0.65 exchange spring magnet

•Preparation of rare earth free Co3C-Co0.35Fe0.65 composite by ball milling.•Co3C-Co0.35Fe0.65 composite exhibited exchange spring magnet.•Energy product could be controlled by variation in hard and soft phases in the composite. A novel magnetic composite material constituted by Co3C (as hard magnetic phase) and Co0.35Fe0.65 (as soft magnetic phase) was synthesized. Ball milling, which is not only easy to use but also industrially viable for large scale production of materials, was used to synthesize both the constituents of the composite and the Co3C-Co0.35Fe0.65 composite itself. Co based phases are chosen because they can be synthesized as both hard and soft magnetic phases by changing appropriate alloying elements. Moreover, the choice of Co3C was made because it is a metastable phase, which can be easily prepared by ball milling. Exchange spring mechanism between the hard and soft magnetic phases in the composite allowed the synergy between (the high coercivity exhibiting) Co3C and (the high saturation magnetization exhibiting) Co0.35Fe0.65 phases, which in turn allowed the realization of an energy product (BHmax) greater than that of the constituents.