Investigation of Ultra-Thin Iron Films
Ultra-thin ferromagnetic films prepared by vacuum evaporation are subject to two effects that can have a profound influence on experimental observations. First, the films tend to oxidize; for example, for an oxygen partial pressure of 10−6 torr at room temperature a monatomic layer of oxygen may form in as short a time as 1 sec. Second, if the film deposition is interrupted at an early stage, it may have an island structure. If the typical island volume V is such that KV, the anisotropy energy, is of the order of or less than kT, the island will be superparamagnetic. This implies that the magnetization vector M S V, where M S is the saturation magnetization, will undergo a kind of Brownian rotation with a relaxation time that may be short relative to the measurement time. Both of these effects will tend to simulate a decreased saturation magnetization and Curie temperature .
KeywordsCurie Temperature Hyperfine Field Metallic Iron Brownian Rotation Island Structure
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