A TOF SIMS-5 by ION-TOF operating with pulsed 25 keV Bi+ for analysis and 2 keV Cs+ for sputtering was used to study depth compositional changes in near-surface layers of permalloy (iron-nickel) blades after treatment by pulsed nitrogen plasma directly in sealed reed switches. The formation of 350 nm-thick oxy-nitride coating in the contacting region of the blades was observed. It was found that the origin of this coating cannot be explained just by nitrogen and oxygen diffusion inside the treated material. Rather, cathode sputtering and re-deposition of sputtered products, thermal decomposition of nitrides and oxides along with sputter-induced surface roughening can also contribute in the formation of the modified layers. (C) 2012 Elsevier B.V. All rights reserved.