From the history of the development of permanent magnetic materials, at the end of nineteenth Century the use of carbon steel, magnetic energy product (BH) max (a measure of permanent magnet storage physical quantity of the magnetic energy density (1MGOe) deficiency, while the foreign high Optoma trillion) mass production of Nd-Fe-B permanent magnetic materials, magnetic energy product has reached more than 50MGOe. In this century, the remanence Br of the material has been improved very little, and the improvement of the energy product is due to the improvement of the coercive force Hc. The coercivity increased, mainly due to that understanding of the nature and high magnetocrystalline anisotropy compounds, and preparation technology progress.
At the beginning of twentieth Century, people mainly use carbon steel, tungsten steel, chromium and cobalt for permanent magnetic materials. At the end of the 1930s, the successful development of AlNiCo permanent magnetic materials made it possible for the large-scale application of permanent magnet materials. In 50s, the emergence of barium ferrite not only reduced the cost of permanent magnets, but also widened the application range of permanent magnets to the high frequency field. By 60s, the emergence of rare earth cobalt permanent magnets has opened up a new era for the application of permanent magnets.
