Ceramic (Ferrite) magnets are susceptible to demagnetization when exposed to temperature extremes. There are grades which have better resistance to high and low temperatures, but several factors will dictate the performance of the Ceramic magnet. One of the most pertinent variables is the geometry of the magnet or magnetic circuit. Magnets which are thin relative to their pole cross-section (Magnetic Length / Pole Area) will demagnetize easier than magnets which are thick. Magnetic geometries utilizing backing plates, yokes, or return path structures will respond better to temperature changes. The maximum recommended operating temperatures listed on the Ceramic magnetic characteristics page does not take into account all geometry conditions.
Caution when using Ceramic magnet in the cold:
Unlike Neodymium, Samarium Cobalt, and Alnico, Ceramic magnets have a Positive Temperature Coefficient for the Intrinsic Coercive Force (Hci) (β). This means that as the temperature increases the magnet may exhibit an increase in net field. This is up to a certain point and the degree of increase is dependent upon the geometry of the magnet. The converse is also true and this is where some designs may have issues. As a Ceramic Magnet experiences a temperature decrease, the net field decreases. This is unlike all other commercial magnet alloys which experience a net field increase when the temperature decreases. Applications where failures may occur could be sensor trigger when the field is not sufficient to trigger a sensor in colder climates. Refer to the Available Ceramic Magnet Grades section of our website for specific thermal performance.
Please contact a Dura team member for Ceramic Magnet design assistance when temperature extremes are involved in your application.