EFFECTIVE FIELDS IN MAGNETIC THIN FILMS: APPLICATION TO THE Co/Cu AND Fe/Cr SYSTEMS

摘要

The description of magnetic properties associated with the behavior of ultrathin structures can be simplified significantly compared with that for bulk materials. Ultrathin layers lose their internal magnetic degrees of freedom. All atomic magnetic moments across the film thickness are parallel because of the very strong exchange interactions between spins, and consequently the total magnetic moment of the film is given by a simple algebraic sum of all of its constituent atomic moments. Ultrathin films are essentially giant magnetic molecules which can have magnetic properties different from those in the bulk. This simple picture can be quantified by employing the Landau-Lifshitz (L-L) equations of motion to describe the behaviour of the magnetization. Since a system consisting of only a few atomic layers is being considered, it is useful to start with the L-L equation of motion for a single atomic magnetic moment which is located in the ultrathin film,