Preparation and magnetic properties of Fe-N thin films by the plasma evaporation method.

Abstract

The saturation magnetization, Ms of films evaporated in N2 atmosphere and in N2 plasma was carefully investigated. The films, which were evaporated in N2 atmosphere by using the alumina crucible as a deposition source, had nearly the same Ms value of about 210 emu/g as that of pure Fe, and were found by X-ray diffraction to contain no iron nitrides. The existence of N, N2+ and N2* produced by the discharge for plasma evaporation, the electron beam by E-gun and the catalysis on W-filament is necessary to obtain Fe-N films. Ms of the films, which were evaporated in weak plasma (Vg=50 V, Ig=O.1A) and by a low deposition rate (R= 1.0Å/s), increased with decreasing the film thickness. The high-moment phase of Fe16N2 could be produced under the following conditions, (1) low density N, N2+ and N2* exist in the reactive gas, (2) the thickness of the film is smaller than about 500Å.