History and evolution of ferriteHistory and evolution of ferrite magnets China's first exposure to ferrite was a natural ferrite found in the fourth century B.C., magnetite (Fe3O4), from which the compass was made. With the development of radio technology in the 1930s, ferromagnetic materials with low loss at high frequencies were urgently required. However, the resistivity of ferric tetroxide is very low, which cannot meet this requirement. In 1933, Tokyo Institute of Technology first created a permanent magnetic material containing cobalt ferrite, which was called OP magnet at that time. In the 1930s and 1940s, France, Japan, Germany, the Netherlands and other countries successively carried out ferrite research work, among which the Dutch Phillip Laboratory physicist J.L. Snooker in 1935 to develop a variety of spinel structure with excellent properties of zinc containing soft magnetic ferrite, in 1946 to achieve industrial production. In 1952, J.J. Venter et al. developed a permanent magnetic ferrite with BaFe12O19 as the main component. This ferrite has a similar hexagonal structure to the four VHF magnetic ferrites studied by G.H. Junker et al. in this chamber in 1956. In 1956, E.F. berto and f. fora reported the results of ferromagnetic Y3Fe5O12. The substitution ions Y include rare earth ions such as Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Because the crystal structure of these magnetic compounds is the same as that of natural mineral garnet, it is called garnet structure ferrite. Up to now, except for the ferrite material with amorphous structure obtained by the ultra-rapid cooling method by Mitsugimoto in Japan in 1981, from the point of view of crystal chemistry, there are no crystal structures beyond the above three types. Most of the work done is modified and further studied for new applications.
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