Compositional inhomogeneity in electroless-deposited CoNiP films studied by spin-echo Co-59 nuclear magnetic resonance

A compositionally inhomogeneous state in electroless-deposited CoNiP films with perpendicular magnetic anisotropy is investigated using spin-echo Co-59 nuclear magnetic resonance (NMR), focusing on its correlation with magnetic properties. Bf adjusting pH of the electroless-deposition bath-films were prepared which possess almost the same average composition (Co42Ni50P8) and crystal orientation, but the differing values of coercivity (H-c). By analyzing the shift in peak resonance frequency of NMR spectra of the CoNiP films with respect to that of bulk CoNi alloys, we observed the formation of a compositionally inhomogeneous slate in the film which possesses high H-c of 2600 Oe, whereas formation of inhomogeneities was not observed for the low-H-c films. By assuming that a Go-enriched ferromagnetic component detected by NMR was separated from a non-magnetic amorphous NI-P component, we found that the high-H-c film consists of Co42Ni26 and Ni24P8. Moreover, the results of high spatial resolution X-ray microanalysis on the high-H-c film showed a tendency that the Go-enriched ferromagnetic component segregates to the center of grains and the Ni-P non-magnetic component segregates to grain boundaries. Such evidence indicates that compositional inhomogeneities could be one of the origins of high-H-c in CoNiP films.