Magnetic Critical Behavior of γ-Fe/Cu Multilayer

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Abstract
Ferromagnetic moment, a magnetic critical exponent β and Curie temperature (TC) of γ-Fe/Cu multilayer (0.8 to 7.2 ML Fe thickness) prepared by the molecular beam epitaxy (MBE) method have been investigated. The crystal structure of γ-Fe layer is distorted tetragonally (c/a>1) for the Fe thickness less than 4.5 monolayer (ML) and cubic for thicker films. Magnetization (M) of γ-Fe is increased with decreasing Fe layer thickness because of the increase of the ratio of high spin state γ-Fe atoms to total Fe atoms at interfaces. A critical exponent in a relationship M/MS = (1-T/TC) β, is estimated to be 0.30±0.02. TC is decreased with decreasing Fe layer thickness. The behavior is explained by taking into account of the number of nearest neighbor Fe atoms around an Fe atom.