NEWS

Below the Curie temperature, there are many small regions within a ferromagnetic or ferrimagnetic material that each have a spontaneous magnetic moment, and the magnetic moments are paired. The direction of their arrangement is disordered. If no magnetic field is applied for magnetization, the overall magnetic moment is zero. These small areas are called magnetic tiles

There is a strong "exchange coupling" between adjacent electrons in ferromagnetism. In the absence of an external magnetic field, their spin magnetic moments can be "spontaneously" aligned in tiny regions. It rises up to form a small area of spontaneous magnetization, which is called a magnetic tile. In an unmagnetized ferromagnetic substance, although each magnetic tile has a definite spontaneous magnetization direction and has great magnetism, the magnetization directions of a large number of magnetic tiles are different, so the whole ferromagnetic substance is not magnetic.

When the electromagnet is in the external magnetic field, the volume of the magnetic tiles whose spontaneous magnetization direction and the direction of the external magnetic field form a small angle will expand with the increase of the external magnetic field, and the magnetization direction of the magnetic tiles will further turn to the direction of the external magnetic field.