Soft magnetic properties of nanocrystalline Fe-Hf-C-N films

Fe-Hf-C-N films with excellent soft magnetic properties were fabricated by Ar+N2 reactive sputtering for the first time. The newly developed films were found to have better soft magnetic properties than those of Fe-Hf-C or Fe-Hf-N films. The best magnetic properties achieved in this work are Hc of 0.15 Oe, μeff of 8200, and 4πMs of 17 kG. The thermal stability of the Fe-Hf-C-N films was also found to be excellent, e.g., Hc was less than 0.3 Oe and μeff was about 4000 for the films annealed up to 700 °C. It was observed by transmission electron microscopy that the films consisted of two phases: a fine crystalline α-Fe phase whose grain size is about 6 nm, and Hf(C,N) precipitates with a size of less than 2 nm. The fine grained α-Fe structures, together with finely dispersed Hf(C,N) precipitates, is considered to be one of the main factors for the excellent magnetic properties and thermal stability.