Iron oxide films were synthesized by pulsed-DC magnetron sputtering from a metallic target in Ar and O2 gas mixtures. Plasma emission monitoring was implemented to accurately control the metalto-oxygen ratio in the coating through the chemical state of the iron target. The intensity of the Fe* emission line was maintained at a given value (setpoint) in regulating the introduced oxygen flow rate. In addition, the oxidation rate of the growing film was adjusted by controlling the oxidationto-deposition rate ratio as a function of the position of the substrates relative to the magnetron axis.The iron oxide films were characterized by X-ray diffraction, UV-VIS spectrophotometry, electrical measurement and vibrating sample magnetometry. In addition to the crystallization of 2 pure hematite and magnetite phases, both phases coexist in a transition domain for a short range of setpoint depending on the oxidation-to-deposition rate ratio. The electrical, optical and magnetic behaviors of the FeOx films suggest that the relative proportion of phases can be tailored in this range. The FeOx film behaviors can then be tuned from the hematite semi-conductor properties to the semi-metallic magnetite properties.
a b s t r a c tThe crystalline and magnetic properties of micron thick magnetron sputtered Co 1 À x Cr x and Co 1 À x Ni x alloy films are analyzed in the view of their implementation as semi-hard magnets. All of the tested films crystallize in an hcp lattice, at least up to 35 at% of alloying elements (Cr or Ni). The structural study shows that the ratio of hcp phase with [0001] axis orientated perpendicular to the film as compared with in-plane orientation increases (resp. decreases), when Ni (resp. Cr) concentration increases independently of the post-annealing temperature. The orientation of the magnetization results from the competition between the demagnetization field which tends to align the magnetization in plane and the crystalline anisotropy which tends to maintain the magnetization along the [0001] axis. Interestingly, we find that, although Co and Ni are very similar atoms, Co 1 À x Ni x alloys crystalline anisotropy can be strongly increased and reach up to twice the anisotropy of the best Co 1 À x Cr x alloy, while maintaining a magnetization at saturation above 1200 kA/m. The thermal stability of the structural and magnetic properties of both alloys is demonstrated for an annealing temperature up to 300°C.
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