A Brief History Of The Development Of Magnets

- Jul 19, 2020-

5,000 years ago, humans discovered natural magnets (Fe3O4)    2300 years ago, Chinese du people grind natural magnets into a spoon shape and place them on a smooth surface. Under the influence of geomagnetism, the spoon handle guides, which means "Sinan". The world's first guide instrument.   1000 years ago, the Chinese used a magnet and an iron needle to friction magnetize, making the world's earliest compass.   Around 1100, China combined the magnet needle and the square lambda plate into a whole to become a magnet-type compass for navigation.  1405-1432 Zheng He started the great pioneering work of navigation in human history by using the compass.   1488-1521 Columbus, Gamma, Magellan made world-famous nautical discoveries with the aid of a guide device from China.   1600 Englishman William Gilber published the monograph "Magnet" on magnetism, repeating and developing the knowledge and experiments of previous people on magnetism.  1785 French physicist C. Coulomb used torsion to establish the "Coulomb's law" that describes the force between electric charges and magnetic poles.   1820 Danish physicist H.C. Oersted discovered that electric current induces magnetic force.  1831 British physicist M. Faraday discovered the phenomenon of electromagnetic induction.  1873 British physicist J.C. Max completed a unified electromagnetic theory in his monograph "On Electricity and Magnetism".   1898-1899 French physicist P. Curie discovered that ferromagnetic substances become paramagnetic at a certain temperature (Curie temperature).   1905 French physicist P.I. Langevin explained the change of paramagnetism with temperature based on the theory of statistical mechanics.  

Rare Earths Periodic_Table

In 1907, French physicist P.E. Weiss proposed the molecular field theory, which extended Lang Zhivin's theory.   1921 Austrian physicist W. Pauli proposed the Bohr magneton as the basic single λ of the atomic magnetic moment. American physicist A. Compton proposed that electrons also have a magnetic moment corresponding to spin.   In 1928, British physicist P.A.M. Dirac perfectly explained the intrinsic spin and magnetic moment of electrons with relativistic quantum mechanics. Together with the German physicist W. Heisenberg, he proved the existence of the exchange force derived from static electricity, laying the foundation of modern magnetism.   In 1936, the Soviet physicist Lang Dao completed the masterpiece "Theoretical Physics Course", which contains a comprehensive and wonderful chapter on modern electromagnetics and ferromagnetism.  1936-1948 French physicist L. Nair proposed the concepts and theories of antiferromagnetism and ferrimagnetism, and deepened his understanding of the magnetism of matter in the following years of research.   1967 The Austrian physicist K.J. Snaiter, a physicist in the United States, discovered the rare earth magnet (SmCo5) with an unprecedentedly high energy product under the guidance of quantum magnetism, thus opening a new chapter in the development of permanent magnet materials.   In 1967, Strnat of Dayton University, USA, developed a samarium-cobalt magnet, marking the arrival of the era of rare earth magnets.  1974 The second generation of rare earth permanent magnet-Sm2Co17 came out.  1982 The third generation of rare earth permanent magnet-Nd2Fe14B came out.