A three-dimensional finite element model was performed to study the magnetization reversal of (CexNd1-x)2Fe14B nanocomposite permanent magnets. The influences of volume fraction, width and performance parameters of the grain boundary (GB) composition on the coercivity were analyzed by the method of micromagnetic simulation. The calculation results indicate that the structure and chemistry of GB phase play important roles in Nd2Fe14B-based magnets. An abnormal increase in the value of coercivity is found to be connected with the GB phase, approximately when the percentage of doped cerium is between 20% and 30%. While the coercivity decreases directly with the increase in cerium content instead of being abnormal when there is no GB phase in magnets at all or the value of magnetocrystalline anisotropy or exchange integral is too large.

MM14Fe79.9B6.1 magnets were prepared by conventional sintering method. The Curie temperature of the sintered MM2Fe14B magnet was about 210 °C. When the sintering temperature increased from 1010 °C to 1030 °C, the density of the magnet increased from 6.85 g/cm3 to 7.52 g/cm3. After the first stage tempering at 900 °C, the (BH)max and Hcj had a slight increase. The maximum value of (BH)max = 7.6 MGOe and Hcj = 1080 Oe was obtained when sintered at 1010 °C and tempering at 900 °C, respectively. The grain size grew very large when the sintering temperature increased to 1050 °C, and the magnetic properties deteriorated rapidly. La reduced by ∼ 7.5 at. % in grains, which is almost equal to the increased percentage of Nd. That is mainly because La-Fe-B is very difficult to form the 2: 14: 1 phase.

Using 3D micromagnetics package OOMMF, the ground states of Ce2Fe14B amorphous nanodisks with different dimensions, initial magnetization states and magnetocrystalline anisotropy constants (K) in zero external field were investigated. The simulations indicate that the disk size is the decisive factor in determining magnetic configurations. A diagram is constructed to bring out the dependence of the different equilibrium states on the disk thickness and diameter. When the ratio of thickness (T) to diameter (D) is smaller than 1, the vortex state is energetically more favorable than other states and the eigenfrequency of vortex approximately proportional to (T/D)1/2. A variety of magnetization distributions of ground states for different anisotropy strengths is obtained. The result shows the magnetocrystalline anisotropy not only shrinks or broadens the vortex core but also induces an out-of-plane magnetization component both at the edge and the center of disks. When the K strength reaches a threshold value, there is a transition from vortex state to Bloch-type Skyrmion state which suggests the possibility of Skyrmion in rare-earth materials. In addition, in the system with specific aspect ratio and low intrinsic anisotropy, the vortex domain can always be sustained under various initial conditions. Meanwhile, the existence of stable vortex domain is found by experimentation in amorphous Ce-Fe-B ribbons which is in good agreement with the simulation result.