Hardferrite magnets:

Ferrite magnets are sintered permanent magnets composed of Barium or Strontium Ferrite. This class of magnets, aside from good resistance to demagnetization, has the popular advantage of low cost. The corrosion resistance of Ferrite is considered “excellent”, and no surface treatments are required.

Ferrite magnets can be produced isotropically or anisotropically. Isotropic grades are not oriented and can be magnetized in any direction, although some degree of greater magnetic strength will be found in the pressing dimension, usually the shortest dimension. Anisotropic grades are oriented in the manufacturing direction, and must be magnetized in the direction of orientation.

Due to their low cost, Ferrite magnets enjoy a very wide range of applications, from motors and loudspeakers to toys and crafts, and are the most widely used permanent magnets today.

Ferrite magnets are very hard and brittle, and require specialized machining techniques. Moreover, they should be machined in an unmagnetized state.