THERMAL-DIFFUSION OF IRON INTO A COPPER(100) CRYSTAL STUDIED BY AUGER-ELECTRON SPECTROSCOPY (AES)

Magnetism in ultra-thin epitaxial layers of iron on copper substrates has generated considerable recent interest. The complexity of the magnetic behaviour is intimately related to the structural properties of the films not simply in terms of the lattice strain at an atomic level, but also through gross structural features like the degree of ordering and presence of defects. These structural issues may be one source of the existing controversy regarding the magnetic properties of the films. We have studied interdiffusion between the film and substrate using Auger electron spectroscopy (AES) complemented by AES/argon depth profile analysis. The interdiffusion threshold is less than 410 K for the Fe/Cu(1 0 0) surface and the results show evidence for two diffusion pathways: one fast and one slow. The results shed light on the interpretation of magnetic and structural measurements of earlier experiments. A study has also been conducted for the Co/Cu(1 0 0) system. In general the growth characteristics of this system are better understood and the AES results give an interdiffusion threshold of again approximately 410 K, but in contrast with the iron films, reveal only a single diffusion mechanism with a slow time scale. © 1989.