Abstract Cobalt carbides nanoparticles have great potential as novel materials in magnetic fields. However, it is difficult to synthesize single phase cobalt carbides, especially Co3C. In this paper, we propose a one‐pot wet‐chemistry approach to synthesize single phase ferromagnetic Co3C without using any alkali as nucleation solvent. The particle size of Co3C nanoparticle is about 3 nm. The magnetic properties of Co3C nanoparticles are measured at 300 K from –30 to 30 kOe. Compared with Co2C, Co3C exhibits a large saturation magnetization of 46.1 emu g–1 and a high coercivity of 1.5 kOe. Small amount of carbon and small particle size of the Co3C nanoparticle are believed to contribute to large magnetization and high coercivity. Magnetic measurements also reveal the spin glass behavior caused by the small Co3C nanoparticle at the spin freezing temperature of 43 K. This work provides a facile method to synthesize single phase Co3C nanoparticle which is applicable in magnetic field.
