According to the shape of the hysteresis loop, ferromagnetic materials can be divided into two categories: soft magnetic materials and hard magnetic materials.
The hysteresis loop of soft magnetism is narrow, remanence Br and coercive force Hc are both small.
Due to the high permeability of soft magnet, it is suitable for manufacturing iron cores of motors and transformers.
The commonly used soft magnet includes cast iron, hot-rolled silicon steel sheet for electrical purposes (gb5212-85), cold-rolled electrical steel strip (gb2521-88), hot-rolled silicon steel sheet for household appliances, soft magnetic alloy strip, pure iron bar for electrical purposes and so on. So what is the difference between hard and soft magnetic materials?
The hysteresis loop width, remanence Br and coercive force Hc of hard magnetism are all large.
Due to the large remanence Br, hard magnet can be used to make permanent magnets, so it is also called permanent magnetic materials.
Generally, remanence Br, coercive force Hc and magnetic energy product (BH) max are three indicators that characterize the properties of permanent magnetic materials.
Hard magnetic (permanent magnet) materials include hysteresis alloy cold-rolled strip (GBn171-82), iron-cobalt-vanadium permanent magnet alloy (GBn172-82), iron-cobalt-molybdenum hysteresis alloy hot-rolled bar (GBn173-82), cast aluminum Nickel-cobalt and powder sintered Al-Ni-Co permanent magnet alloy (GBn4753-84), sintered and bonded permanent magnet ferrite material (SJ/T10410-93) and so on.
In addition, there are rare earth permanent magnet materials as hard magnetic materials used in motors, such as samarium cobalt, samarium praseodymium cobalt, neodymium iron boron, and rare earth cobalt.