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‘‘Giant’’ magnetoresistance ratios have been measured at room temperature in single layer Co–Ag alloy thin film. The effect has been observed over a broad range of Co concentrations with a maximum as-deposited MR ratio of ≥22% (at x=0.38). The effects of two annealing sequences have also been studied. The MR ratio generally increases on annealing reaching a maximum of ∼28% (at x=0.38) after the second anneal.

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Giant magnetoresistance in granular alloy thin films prepared by co-sputtering as well as in quasi-granular disordered multilayers has been modeled with relative ease using a simple scattering concept appropriate to superparamagnetic films and involving the Langevin function. The model has been applied to both as-deposited and annealed samples with the result that approximate sizes of spin clusters may be determined.

The growth and microstructural evolution of Al/Ni and Ni/AI bilayer thin films have been investigated as a function of Al and Ni layer thickness and thermal treatment by transmission electron microscopy. Studies were also made of Al and Ni single layers of varying thickness. All films were grown by dc magnetron sputtering using carbon coated Cu TEM grids as substrates. For the bilayers, the Al thickness was fixed at either 3.5 or 7.0 nm while the Ni thickness was varied systematically from 3.2 to 12.8 nm. Deposition sequence significantly influenced bilayer microstructure even in as-deposited samples. Al/Ni bilayers generally exhibited a finer microstructure than Ni/AI. In the 3.5 nm Al/Ni bilayers no conclusive electron diffraction evidence was found for elemental Al while for the reverse sequence both Al and NiAl3 diffraction rings were found. In the 7.0 nm Al/Ni bilayers diffraction rings due to Al were observed. The reverse sequence again produced both Al and NiAl3 diffraction rings. Interestingly, diffraction rings due to the Ni layers were found for all samples but were consistently measured at positions corresponding to a 2.5–3.5% increase in interplanar spacing. Annealing at 385°C produced evidence for generalized grain growth and strong accentuation of the electron diffraction rings due to the NiAl3 phase. Again, deposition significantly influenced annealed bilayer microstructure. For the Al/Ni sequence annealing produced polycrystalline N1AI3 island-like structures, while for Ni/AI bilayers, annealing promoted the growth of small NiAl3 crystals uniformly distributed in the film.