The Difference Between Maximum Working Temperature and Curie Temperature of Magnet
Maybe some people think the maximum working temperature of magnet is same as its Curie temperature. Actually, this is a mistake.
The magnetic material can be divided into 5 kinds: ferromagnetism, ferrimagnetism, anti-ferromagnetism, paramagnetism, diamagnetism. Iron, Cobalt and Nickel are ferromagnetic material, also permanent magnets.
For ferromagnetic materials, when the temperature rises beyond a certain point, there is a second-order phase transition and these materials can no longer maintain spontaneous magnetization. These materials will transform into paraferromagnetism state, so its ability to be magnetized or attracted to a magnet disappears. This certain point called the Curie temperature or Curie point.
The maximum working temperature refers to the temperature at which a magnet begins to lose its strength if continue heated. This loss of strength in a given time may only be minimal, less than 5%, when the magnet returns to room temperature. It should be noted that different country have different standard.
As for same magnet, the Curie temperature will much higher than its Maximum working temperature.
Different type of permanent magnet has its own Curie temperature and maximum working temperature. Please check below table:
The Curie temperature have deeply influence on magnet’s maximum working temperature. The Curie temperature only depends on the component of magnet. In order to get higher maximum working temperature, the manufactures need to add Cobalt, Dysprosium, Terbium elements to promote the Curie temperature of magnet.
The maximum working temperature is not only influenced by its Curie temperature, but also related to intrinsic coercivity and working condition.