With the development of society, magnets are more and more widely used, from high-tech products to the simplest magnetic packaging. At present, Nd-Fe-B magnets and ferrite magnets are most widely used. From the development history of magnets, man-made magnets appeared in the 18th century, but the process of manufacturing stronger magnetic materials is very slow. At the end of the 19th century and the beginning of the 20th century, carbon steel, tungsten steel, chromium steel and cobalt steel were mainly used as permanent magnet materials. In the late 1930s, the successful development of alnico magnet made the large-scale application of magnet possible. In the 1950s, the emergence of barium ferrite magnet not only reduced the cost of permanent magnet, but also widened the application range of permanent magnet materials to the field of high frequency. In the 1960s, the emergence of samarium cobalt permanent magnet opened up a new era for the application of magnets. In 1967, SmCo magnets were developed by strnat of Dayton University in the United States, marking the arrival of the era of rare earth magnets. Dilute ten permanent magnets have experienced the first generation of SmCo5, the second generation of precipitation hardening Sm2Co17, and developed into the third generation of Nd-Fe-B permanent magnet materials. So far, magnetic technology has developed rapidly, and strong magnetic materials also make components more miniaturized.
Development history of foreign magnets
People really understand magnets and magnetism from the inside and in theory from the near ancient times, starting with the interaction between electric charge and magnetic pole discovered by French physicist Coulomb in 1785 and the familiar "Coulomb's law". It opens the door to people's understanding of magnets. In the following 300 years, we have a deeper understanding of magnets and magnetism. Among them, the landmark is:
In 1831, the British physicist Faraday discovered the phenomenon of electromagnetic induction. This is a person and phenomenon we are very familiar with. We have read "Faraday electromagnetic induction" more than once.
In 1973, another physicist, Maxwell, unified the electromagnetic theory. His work is "on electricity and magnetism". In our physics class in high school, we often see characters and books.
In 1899, Curie, a French physicist, discovered that ferromagnetic substances would have a phenomenon paramagnetism under the Curie temperature named after him.
In 1905, the sixth year after Curie discovered paramagnetism, a scientist Lang Ziwan used the theory of statistical mechanics to explain Curie's paramagnetism with temperature.
In 1907, two years after Lang Ziwan explained paramagnetism, French physicist Weiss expanded Lang Ziwan's theory with his molecular field theory.
From this timetable, it is not difficult to see that our human understanding of magnets such as permanent magnets has entered a fast lane in the middle of the 19th century. By the beginning of the 20th century, it had been reached, and a discovery and a theory came out every few years.
