Micromagnetic Simulation On Coercivity Of High Abundance Rare Earth Permanent Magnet Ce_1-xMg_xCo₃

As one of the newly discovered high abundance rare earth permanent magnets,Mg doped Ce Co₃alloy has attracted extensive attention for its strong ferromagnetism,large magnetocrystalline anisotropy,low cost and good hydrogen evolution performance.However,the coercivity potential of Ce_1-xMg_xCo₃magnet has not been fully exploited,which limits its practical application to a certain extent.It is well known that the coercivity of samples is closely related to the microstructure.Clarifying the dependence between microstructure and coercivity not only has important theoretical significance,but also has important application value for the design of higher performance magnets.In order to fully tap the permanent magnetic properties of high abundance rare earth permanent magnet,the magnetization behavior of the system is simulated by micromagnetism,the dependence of macro magnetic properties on grain size,precipitation and different microstructure is analyzed,and the performance parameters related to coercivity of Ce_1-xMg_xCo₃permanent magnet are found.This work provides an important reference for promoting the balanced utilization of rare earth in China.The main research contents of this paper are as follows:（1）Firstly,the effect of average grain size on the coercivity of Ce_1-xMg_xCo₃polycrystalline permanent magnet is simulated.The Voronoi polycrystalline model and cubic nanowire model were established respectively to simulate the micromagnetism of polycrystalline samples with different grain sizes.By analyzing the magnetization behavior and combined with the simulated images under different magnetic fields,the coercivity mechanism is discussed.The results show that under the polycrystalline model of nano disk and nano wire,the coercivity of magnet shows nonlinear size dependence,and the coercivity can reach 1.40～1.45 T when the particle size is about 320 nm.In addition,for the polycrystalline model of nanowires,large coercivity can often be obtained by axial magnetization.（2）The research show that a small amount of Co or Mg Co₂phase precipitates in the Ce_1-xMg_xCo₃sample.Based on this,in order to further analyze the influence of precipitation on the coercivity of magnet,we establish different models to explore the influence mechanism of precipitation on the coercivity of magnet.The precipitation of magnetic phase Co and non-magnetic phase Mg Co₂on the surface of single crystal,inside of single crystal and inside of polycrystalline were simulated respectively.The simulation results show that when there is a small amount of Co magnetic phase in the magnet,the co precipitate often acts as a nucleation defect,which reduces the coercivity of the magnet;When a small amount of non-magnetic phase Mg Co₂is precipitated in the polycrystalline magnet,the coercivity of the magnet can be improved.