Semi-hard magnetism of iron nitride films prepared by double ion beam sputtering

The semihard magnetic properties and crystal structure of iron nitride films prepared by double ion beam sputtering have been investigated. The films consisted of Fe layers and Fe/sub x/N layers bombarded by nitrogen ions during deposition. The films were annealed at 300 degrees C for 3 h after deposition. When the thickness ratio of Fe layers to Fe/sub x/N was adjusted to a value below 10 for films with the appropriate number of pairs of layers, the as-deposited films had coercivity, H/sub c/ of about 100 Oe and saturation magnetization, 4 pi M/sub s/, of about 18 kG. Annealing of films composed of 19 pairs of Fe and Fe/sub x/N layers with a relative thickness ratio of 5 resulted in a large increase in film coercivity from less than 100 Oe before anneal to 500 Oe postanneal. A moderate decrease in film 4 pi M/sub s/ was also seen after the annealing process. X-ray diffractometry showed the presence of zeta -Fe/sub 2/N phase in these films. A moderate decrease of 4 pi M/sub s/ and a marked increase of H/sub c/ may be caused by suppressing the growth of zeta -Fe/sub 2/N crystallites and the short-range irregularity at interfaces between Fe and Fe/sub x/N layers.<
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