5,000 years ago, humans discovered natural magnets (Fe3O4)
Three hundred years ago, the Chinese ground a natural magnet into the shape of a spoon and placed it on a smooth surface. Under the action of the earth's magnetic field, the handle of the spoon is called "Sina", which is the world's first guiding instrument.
1,000 years ago, the Chinese made the world's first compass by rubbing and magnetizing magnets with iron needles.
About 100 years ago, China combined a magnetic needle and an azimuth disk into a magnetometer for navigation.
From 1405 to 1432, Zheng He started the great pioneering work of navigation in human history.
In 1488-1521, Columbus, Gama and Magellan made famous voyages using the compass.
William Gilbert, an Englishman, published his monograph Magnet on magnetism, which developed the knowledge and experiments of ancient Greeks such as Thales and Aristotle on magnetism.
The French physicist c. Coulomb established Coulomb's law, using a torsion pestle to describe the force between an electric charge and a magnetic pole.
In 1820, the Danish physicist H.C. Oster discovered current-induced magnetism.
In 1831, British physicist m. Faraday discovered the phenomenon of electromagnetic induction.
In 1873, British physicist J.C. Maxwell 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).
In 1905, French physicist P.I. Langevin explained the variation of paramagnetism with temperature according to the theory of statistical mechanics.
In 1907, French physicist P.E. Weiss proposed molecular field theory, which extended Langevin's theory.
In 1921, Austrian physicist W. Pauli proposed that the Bohr magnet is the basic unit of the magnetic moment of an atom. American physicist A. Compton proposed that electrons also have magnetic moments corresponding to their spins.
928 The British physicist P.A. Dirac used relativistic quantum mechanics to perfectly explain the intrinsic spin and magnetic moment of electrons. Together with the German physicist W. Heisenberg, he proved the existence of the exchanging force produced by static electricity, laying the foundation of modern magnetism.
In 1936, the Soviet physicist Daolang completed his magnum opus, The Course of Theoretical Physics, which included a comprehensive and wonderful chapter on modern electromagnetism and ferromagnetism.
Between 1936 and 1948, the French physicist L. Nair proposed the concept and theory of antiferromagnetism and ferromagnetism, and deepened the understanding of matter magnetism in the following years of research.
In 1967, under the guidance of quantum magnetism, K.J. Knight, an Austrian physicist living in the United States, discovered the highest magnetic energy product ever recorded.
Rare earth magnet (SmCo5), thus opening a new chapter in the development of permanent magnet materials.
In 1967, Strnat at the University of Dayton in the United States developed a samarium cobalt magnet, marking the arrival of the era of rare earth magnets.
In 1974, the second generation of rare earth permanent magnet - sm2co 17 came out.
In 1982, Masato Sagawa of Sumitomo, Japan, invented the neodymium magnet, and the third generation of rare earth permanent magnet, nd 2 Fe 14b, came out.
In 1990, Sm-Fe-N, an atomic gap magnet, was introduced.
In 1991, German physicist E.F. Knoelle proposed the theoretical basis of the exchange effect of two-phase composite magnets and pointed out the development prospect of nanocrystalline magnets.
With the development of society, magnets are used more and more widely, from high-tech products to the simplest packaging magnets.
At present, neodymium and ferrite magnets are the most widely used magnets.
From the development history of magnets, from the end of the 19th century to the beginning of the 20th century, people mainly used carbon steel, tungsten steel, chromium steel and cobalt steel as permanent magnet materials.
