Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

Cobalt nitride (Co-N) thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (R-N2) was varied. As R-N2 increases, Co(N), Co4N, Co3N and CoN phases are formed. An incremental increase in R-N2, after emergence of Co4N phase at R-N2 = 10%, results in a linear increase of the lattice constant (a) of Co4N. For R-N2 = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co4N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M4N) have been theoretically predicted. Incorporation of N atoms in M4N configuration results in an expansion of a (relative to pure metal) and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M4N compounds. Though a higher (than pure Fe) magnetic moment for Fe4N thin films has been evidenced experimentally, higher (than pure Co) magnetic moment is evidenced in this work. (C) 2015 Author(s).