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Several series of thin films (∼3000 Å) were fabricated by coevaporation of Co and Ag in a dual e-beam UHV system at substrate temperatures, TS, between 300 and 500 K. The composition was varied between 23 and 54 at. % Co. The maximum measured magnetoresistance was 31% at room and 67% at nitrogen temperature. Magnetization and Rutherford backscattering measurements showed that the Co and Ag atoms are completely segregated for films deposited at TS≥400 K. The magnetoresistance (MR) and magnetization curves have been analyzed taking into account both the paramagnetic (PM) and ferromagnetic (FM) contributions that are observed to be present. The films having ≤32 at. % Co are entirely paramagnetic. The fraction of Co atoms in the ferromagnetic component increases monotonically with increasing TS and/or at. % Co. The average radii of the PM granules in the films having an MR effect of 25%–31% are ∼20–22 Å with a minimum average separation of ∼10 Å. The large MR values attained in both the PM and FM components are attributed to the small effective domain sizes, ∼40–50 Å. The MR values are large because the MR effect varies inversely as the mean-free-path for magnetic boundary scattering which is the average distance between domain boundaries. The variation of the resistive and magnetic behavior of the films was also studied as a function of the annealing time for an annealing temperature of 300 °C. A striking behavior seen in these films is the long relaxation times when a FM component is present.

The effect of elevated temperature on the structural stability and performance of Mo-Si multilayer mirrors is investigated. Mo-Si multilayers deposited by magnetron sputtering are annealed at temperatures ranging from 200 to 800 °C. A detailed and consistent picture of the thermally induced changes in the microstructure is obtained using an array of complementary measurement techniques including small- and large-angle x-ray scattering and high-resolution electron microscopy. The first significant structural changes are observed at 400 °C, characterized by an increase in the width of the amorphous interlayer regions, as well as the nucleation of microcrystallites of silicide in these regions. At higher temperature the Mo layers transform completely into polycrystalline mixtures of Mo5 Si3 and MoSi2 in both the hexagonal and tetragonal phase. The layers of silicide remain intact but exhibit a structural instability, resulting in severely warped layers surrounded by pockets of amorphous Si and voids. By 800 °C the layered structure is completely destroyed and the composition is predominately tetragonal MoSi2 . The performance of the multilayers as normal-incidence x-ray mirrors is measured and correlated with the observed structural modifications. Finally, our results are compared and contrasted with other annealing studies of the Mo-Si system.

Multilayered structures containing thin (1-12 nm) layers ofW or Mo, alternating with C or Si, have been prepared to produce thin cross-sectional specimens, and direct structural information on the atomic scale has been obtained using an ultrahigh resolution electron microscope. Layer thickness and flatness have been analyzed-the average layer thickness varies by up to 0.6 nm from the average value, and the flatness of the layers depends on the quality of the substrate surface. The degree of crystallinity and crystal orientation wit~in the layers has also been examined. This information should enable more accurate theorettcal models to be proposed for the multilayer materials and their x-ray optical properties. The results for the Mo/Si multilayers suggest a model for their growth when prepared by sputtering.

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