Structure and magnetization of Co 4 N thin film

Highlights: • Nearly perfect Co₄N thin films have been prepared. • Local structure was probed using XANES and EXAFS Co K,L-edge and at N K-edge. • Composition of films measured using SIMS. • PNR measurements suggest higher than pure Co magnetic moment in Co₄N. In this work, we studied the local structure and the magnetization of ${\text{Co}}_4\text{N}$ thin films deposited by a reactive dc magnetron sputtering process. The interstitial incorporation of N atoms in a fcc Co lattice is expected to expand the structure. This expansion yields interesting magnetic properties e.g. a larger magnetic moment (than Co) and a very high value of spin polarization ratio in ${\text{Co}}_4\text{N}$. By optimizing the growth conditions, we prepared ${\text{Co}}_4\text{N}$ film having lattice parameter close to its theoretically predicted value. The N concentration was measured using secondary ion mass spectroscopy. Detailed magnetization measurements using bulk magnetization method and polarized neutron reflectivity confirm that the magnetic moment of Co in ${\text{Co}}_4\text{N}$ is higher than that of Co.