Micro-magnetic Study On The Magnetic Properties Of Dual-principal-phase Nd-Fe-B/Ce-Fe-B Nanocomposites

As a key research project of China's strategic emerging industries,rare earth permanent magnet materials play a pivotal role in industries that require strict magnetic properties,such as clean energy and high-performance motors.However,after long-term development of China's rare earth industry,the utilization of rare earth resources is extremely unbalanced.The scarce resources such as Nd and Dy are over-exploited,but the abundant resources such as Ce are not fully utilized.Therefore,a focus of current research of rare earth permanent magnet materials is the further development and use of high abundance rare earth elements such as Ce.In this thesis,the magnetization reversal process of the dual-phase Nd₂Fe₁₄B/Ce₂Fe₁₄B periodic multilayer film and the Nd₂Fe₁₄B/Ce₂Fe₁₄B core-shell structure nanocomposite rod were simulated by the three-dimensional calculation software OOMMF on the basis of the theory of micro-magnetism method.The remanence,coercivity,and coercivity of the system were been studied.The hysteresis loop and the energy change in the process of magnetization reversal are analyzed,and the coercive force mechanism of the magnet is analyzed,which provides a certain reference for the preparation of high-performance magnets with high Ce content in the future.The main findings are as follows:(1)A dual principal phase Nd₂Fe₁₄B/Ce₂Fe₁₄B periodic multilayer film model was established,and the dual principal phase periodic multilayer films with different orientations were studied,and the influence of the thickness and number of layers on the magnetic properties of the multilayer film was explored.The simulation results show that the coercivity mechanism of the dual principal phase Nd₂Fe₁₄B/Ce₂Fe₁₄B periodic multilayer film is mainly dominated by nucleation.In the studied magnetic layer thickness range,when the total thickness of the magnetic film remains unchanged,increasing the layer thickness gradually reduce the coercivity and maximum energy product of the periodic multilayer film;when the number of magnetic film layers remains unchanged,Increasing the thickness of the magnetic layer will also gradually reduce the coercivity and maximum energy product of the periodic multilayer film;when other conditions are the same,the performance of the parallel-oriented periodic multilayer film is better than that of the perpendicularly-oriented periodic multilayer film.(2)The dual principal phase Nd₂Fe₁₄B/Ce₂Fe₁₄B composite nanorod model was established,and the influence of the diameter,thickness and material of the inner core and outer shell on the magnetic properties of the system was studied.The research results show that for composite nanorods with Ce₂Fe₁₄B as core and Nd₂Fe₁₄B as shell structure,the remanence of composite nanorods increases monotonically with the increase of the thickness of the Nd₂Fe₁₄B shell while keeping the diameter of the inner core constant,but the coercive force and magnetic energy product show a trend of first increasing and then decreasing;the coercivity,remanence and energy product of the composite nanorods will decrease with the increase of the diameter of the Ce₂Fe₁₄B inner core,but the magnitude of the change is relatively small;for composite nanorods with a Nd₂Fe₁₄B as core and Ce₂Fe₁₄B as shell structure,as the thickness of the Ce₂Fe₁₄B shell increases,the coercive force,remanence and magnetic energy product of the composite nanorods decrease monotonously;on the premise of keeping the thickness of the shell constant,with the increase of the diameter of the Nd₂Fe₁₄B inner core,the coercive force,remanence and energy product of the composite nanorods all change very small;the coercivity mechanism of the dual principal phase Nd₂Fe₁₄B/Ce₂Fe₁₄B core-shell composite nanorods is dominated by nucleation.