Magnetism in Oligatomic Films

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Abstract
The magnetic properties of very thin single‐crystal films, consisting of only a few flat, parallel atomic layers, denoted as ``oligatomic films,'' are considered. They are interesting mainly for the dependence of their magnetization and Curie temperature on the thickness, which have been calculated during recent years using the main theories of ferromagnetism. A review is given of the theoretical results, showing strong differences between different theories. Oligatomic films may be used in multilayer experiments to investigate an indirect exchange via the conduction electrons. Methods for preparing oligatomic films of Ni, Fe, Co, and their alloys by epitaxy on Cu single crystals, for testing their structure and for measuring their magnetic properties are discussed. Special attention is given to 48Ni/52Fe (111) films. These were ferromagnetic at least down to 6 Å. Their magnetization as a function of thickness shows agreeable fit to spin‐wave and Green's‐function calculations. A Néel‐type surface anisotropy is detected. Coating the films with Mo instead of Cu affects the magnetization and Curie temperatures of films only slightly, down to 3 layers (6 Å); however, the surface anisotropy is lowered.