The Studies Of Magnetic Properties In Magnetic Multilayer With Complex Interactions

Recently, the critical behaviors of magnetic films are of great interest because of the insight they provide into the fundamental nature of magnetism and technological applications. Here, the improved Monte Carlo (MC) simulation and transfer matrix methods (TM) are developed and the critical behaviors of magnetic thin film with complex exchange interactions are investigated. The main content is described as follows:1. A 4x4 transfer matrix method instead of a 2×2 transfer matrix method has been developed for the films with the nearest neighbor (AW) and next nearest neighbor (NNN) interactions. From the 4×4 transfer matrix equations, we can get all the information about the phase transition temperature of a particular structure. It is suitable for arbitrary exchange constants and number of layers. Moreover, matrix equations determining the transition temperature of the surface and body of the film are also derived.2. We have performed the Monte Carlo simulation to study the phase transition in various systems by using appropriate order parameters. It is found that the FCC systems are predicted to exhibit four different types of ordering at low temperature, which is depending on the relative signs and strengths of the AW and NNN interactions, respectively. While the BCC systems exhibit three kinds of ordering. It is also found that the phase temperature is sensitive to the relative signs and strengths of the AW and NNN interaction. The calculated results derived from the improved 4×4 transfer matrix are consistent with that simulated by MC method.3. Based on MC simulation, the dependence of the phase transition temperature (τc or τN) on both the ratios of surface coupling to inner layers one Js/Jb and the next-nearest coupling to nearest one b, and the size of the system have been studied. It is found that, the magnetic phase diagrams for the surface and inner layers reveal the complex ordered and disordered magnetic states. The phase transition temperature is not only associated with the relative signs and strengths of the AW and ANNN interactions, but also with the value of surface coupling and layers of film. The calculated results derived by TM method are in good agreement with those simulated from MC simulation and well explain the experiment facts, which mean that the improved 4×4 transfer matrix method is effective and applicable.