Enhanced solid solubility in hcp Co(Mo) nanoparticles formed via inert gas condensation

Co–Mo alloy clusters with extended solubility of Mo in hcp Co were produced by inert gas condensation (IGC). While the equilibrium solubility of Mo in hexagonal close-packed (hcp) Co is on the order of 1 atomic percent, the non-equilibrium aspects of IGC resulted in ~ 18 atomic percent Mo dissolved in hcp Co. The extended solid solutions and hcp structure were observed across all of the processing conditions, which included variation of sputtering power and aperture size. There was, however, variation of nanoparticle size and magnetic behavior with processing parameters. The Co(Mo) nanoparticles were ferromagnetic at room temperature. Coercivities of the nanoparticles produced with a 2.5-mm aperture were independent of sputtering power and significantly higher than those of the nanoparticles produced with a 7-mm aperture. The coercivities of the nanoparticles produced with a 7-mm aperture were slightly power-dependent. Overall, there appeared to be a relationship between coercivity and nanoparticle size.