An effect of nitrogen on magnetic properties and microstructure of Fe–Nb–B–N nanocrystalline thin films

Abstract

Fe-Nb-B-N films with good soft magnetic properties were fabricated by ArϩN 2 reactive sputtering. The quaternary films have better soft magnetic properties than that of Fe-Nb-B films. The best magnetic properties are saturation magnetization of 16.5 kG, coercivity of 0.13 Oe and effective permeability of about 5000 up to 10 MHz. It was observed by transmission electron microscopy that the Fe-Nb-B-N thin film annealed at 590°C consisted of three phases: a fine ␣-Fe phase whose grain size is around 7 nm, a Nb-B rich amorphous phase and NbN precipitates with the size of less than 3 nm. The fine grained ␣-Fe structure, together with finely dispersed NbN precipitates and the amorphous boundary phase are considered to be a main factor for the good magnetic properties.