The Preparation And Magntic Simulation Of Nanocomposite Permanent Magnetic Films

Nanocomposite permanent magnetic films with high remanence and large giant energy products have wide application prospect in the information, micro-mechanical, micro-robot, etc. Based on a review of its current condition and development home and abroad, the thesis systematically conducts research on it, in both experiment and computer simulation.In this work for experiments, Nd2Fe14B/α-Fe/Nd2Fe14B sandwich permanent magneitc films were prepared by DC magnetron sputtering and ion sputtering. The influence of annealing temperature and the soft magnetic thickness on the film structure and magnetic properties were studied. The results show that all of as-deposited films are amorphous. With the increase of annealing temperature, the crystalline phase gradually increase, consisting of Nd2Fe14B phase andα-Fe phase, but the c-axis orientation of Nd2Fe14B phase are not obvious. The remanence and coercivity enhance, and then decrease with the annealing temperature increasing, the maximum values are obtained on the condition of 650℃; The coercivity decreases with the increase of the soft magnetic thickness, but the remanence firstly enhance and decrease later.In this work for simulation, based on micromagnetic theory, Nd2Fe14B/α-Fe bilayer films were simulated by three-dimension model. The effects of structure dimensions for hard and soft magnetic thickness on magnetic properties were studied. By the relation between magnetic properties and soft magnetic thickness, the hysteresis loops is rectangle and the bilayer films are in complete exchange-coupling region when the soft magnetic thickness is below the critical point. The remanence and maximum energy products firstly enhance and decrease later with the increase of the soft magnetic thickness, but the coercivity decreases monotonically. By the relation between magnetic properties and hard magnetic thickness, the coercivity firstly enhances greatly with the increase of the hard magnetic thickness, and then changes gently, but the maximum energy products always decreases. The maximum values of the maximum energy products for Nd2Fe14B/α-Fe bilayer films is 686kJ/m3 by estimation.The reasons for poor magnetic properties of Nd2Fe14B/α-Fe/Nd2Fe14B sandwich permanent magnetic films are obtained, through the comparative analysis between the simulation and experimental results. On the one hand, the degree of texture for Nd2Fe14B phase is not high; on the other hand, the soft magnetic thickness greatly exceeds the best exchange coupling size for Nd2Fe14B/α-Fe bilayer films.