Due to the advent of rare earth permanent magnet materials, the performance of ferrite permanent magnet materials has been progressing by leaps and bounds. Rare-earth permanent magnet materials have experienced three stages of development of SmCo5, Sm2Co17 and Nd-Fe-B. Since 1983, the third generation of rare earth Nd-Fe-B material advent, with its excellent performance and rare earth source of NdFeB magnets strong source of magnetism has become the object of attention of researchers in various countries, the current sintered Nd-Fe- B rare earth permanent magnet magnetic energy product has reached as high as 432kJ / m3 (54MGOe), has been close to the theoretical value of 512kJ / m3 (64MGOe), and quickly out of the laboratory, into large-scale production. Nd-Fe-B annual growth rate of about 18% to 20%, accounting for 40% of ferrite permanent magnet material output. However, the main disadvantage of Nd-Fe-B permanent magnets is that the Curie temperature is low (TC≈593K) and the maximum working temperature is about 450K. In addition, the chemical stability is poor, which is easily corroded and oxidized and the price is higher than ferrite. This limits its scope of use.

The current research direction is to explore new types of rare earth permanent magnet materials on the one hand, such as ThMn12 type compounds, Sm2Fe17Nx, Sm2Fe17C compounds, on the other hand is the development of nano-composite rare earth permanent magnet materials. The earliest developed nanocrystalline rare earth permanent magnet alloy is to add certain trace elements such as V, Si, Ga, Nb, Co and so on in the quenched Nd-Fe-B alloy to facilitate the grain refinement and to form nanocrystals, High Br, to achieve the purpose of increasing (BH) max. Recently, Coehoorn and Ding et al. Proposed a new concept of "dual-phase nanocrystalline coupled permanent magnet alloys." This alloy contains at least two major magnetic phases: a soft magnetic phase and a hard magnetic phase, and has a nanostructured microstructure. Generally, the saturation magnetization of the soft magnetic material is higher than that of the permanent magnetic material, and the magnetocrystalline anisotropy of the permanent magnetic material is much higher than that of the soft magnetic material. For example, when the soft magnetic phase and the permanent magnetic phase are compounded in the nanoscale range, It is possible to obtain a new type of permanent magnetic material having both high saturation magnetization and high coercive force with both advantages. At present, nano rare earth permanent magnetic alloys have entered the practical stage, the most commonly used is Nd2Fe14B + α-Fe or Nd2Fe14B + Fe3B alloy. Compared with other ferrite magnets, the nanocrystalline rare earth permanent magnets contain less rare earth metal, so they have better temperature stability and are less resistant to oxidation and corrosion. At the same time the alloy contains more iron, is expected to improve the brittleness and workability of the alloy. In addition, nanocrystalline rare earth permanent magnet alloys have extremely high potential (BH) max values. Therefore, nanometer permanent magnet materials are expected to become a new generation of permanent magnet materials, and have become the hotspot of current research.