The ability of a material to retain magnetism is called magnetic hysteresis or magnetic retention.

Magnetic hysteresis refers to the phenomenon where a magnetic material retains some degree of magnetism after exposure to an external magnetic field. This is due to the alignment of the magnetic domains within the material, which can be “locked in” after exposure to a strong magnetic field.

The level of magnetism that a material can retain is measured by its magnetic coercivity, which is the amount of magnetic field required to demagnetize the material thoroughly. Materials with high coercivity are better at retaining magnetism. They are often used for permanent magnets, while materials with low coercivity are more easily demagnetized and are used for temporary magnets.

Magnetic retention is essential in many applications, such as producing magnetic data storage devices like hard drives or credit card strips. The material’s ability to retain magnetism over time is crucial to the device’s function.