Polycrystalline Fe3O4 films have been prepared by reactive sputtering at room temperature. Transmission electron microscopy images show that the films consist of quite uniform Fe3O4 grains well separated by grain boundaries. It was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupled grain boundaries dominates the transport properties of the films. Magnetoresistance (MR) {=[ρ(H)-ρ(0)]/ρ(0)} shows linear and quadratic magnetic-field dependence in the low-field range when the field is applied parallel and perpendicular to film plane, which is similar to the behaviors observed in the epitaxial Fe3O4 films consisting of a large raction of antiferromagnetic antiphase domain boundaries. At 300K, the size of the MR reaches 27.4% under a 50-kOe magnetic field, which is a very large MR for polycrystalline Fe3O4 films.

The structural characterization of heat-treated CN films fabricated by dual-facing-target sputtering for soft X-ray multilayer mirrors was performed by means of X-ray diffraction (XRD), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS). The XRD analyses indicate a graphization process in the CN films during thermal annealing. The Raman analyses imply that the primary bonding in the CN films is sp2. In other words, the formation of the sp3 bonding in the CN films can be suppressed effectively by doping with N atoms, and thus the thickness expansion resulting from the changes in the density of CN films during annealing can be decreased considerably. This result is also clarified by the increased conductivity measured. The XPS results give the information of the existence of the strong covalent bonding between N and C atoms, which can slow down the tendency of the structural relaxation during annealing. These results suggest that CN films suitable for soft X-ray multilayers used at high-temperature environments can be obtained by reactive dual-facing-target sputtering. With the low-angle X-ray diffraction measurements, we do observe the enhanced thermal stability of CoN=CN multilayers.

The effects of Co addition on the structure and the saturation magnetization of Fe16N2 were investigated. Enhancement of the formation of Fe16N2 phase by Co addition was observed. Films with 5-25 at% Co contents deposited at proper conditions exhibit a high saturation magnetization up to the range of 2.5-2.7 T. The saturation magnetization of (Fe, Co) 16N2 alloys phase is expected to be 2.8-2.9 T, which is as large as that of Fe16N2. This demonstrates that proper Co addition does not induce notable changes in the high saturation magnetization of the Fe16N2.

The effect of aging on Co/C multilayer x-ray mirrors is presented. One significant result is the enhancement of the reflectivity at grazing incidence with time for the Co/C multilayers with C-on-top stored in air or argon and Co-on-top stored in argon. This can be interpreted in terms of a Co-C phase-separation at Co-C interfaces due to the positive enthalpy of Co-C mixing. Results also show that oxidation of the surface of Co-on-top Co/C multilayers plays an important role in the decrease of reflectivity. The oxidation can be prevented by storing the multilayers in an oxygen-free atmosphere or by depositing amorphous carbon as the top layer. The reflectivity of tarnished multilayers can be restored by removing the oxides by wet chemical methods.

Fe-N gradient films were prepared with a facing targets sputtering system. During deposition, the nitrogen pressure increased linearly up to a value, which is called the "ultimate pressure." Composition profiles, microstructure, magnetic properties, and corrosion resistance of the films were investigated by various methods. The experimental results indicate that the Fe-N films possess some composition and structural gradients. The Fe concentration decreases from the substrate to the film surface from 100 to 66 at. %. The phases α"-Fe16N2, γ'-Fe4N, ε-FexN(2<x≤3) and ζ-FeN are present in the gradient films at different depths. Ms under the ultimate nitrogen pressure of 0.05 Pa has a value of 1803 emu/cc which is higher than that of bulk iron, this is attributed to the presence of Fe16N2. Increasing further the ultimate nitrogen pressure, Me decreases monotonically. The corrosion resistance of the gradient film with higher nitrogen concentration near the surface is good enough t'or magnetic recording heads. ~ 1995 American Institute of Physics.