What is remanence?
Remanence, or residual magnetism, is the magnetization that remains in a ferromagnetic material (such as iron) after an external magnetic field has been removed. Remanence occurs within ferromagnetic materials and is the flux density that a magnetic material retains. High values of remanence and coercivity are especially desirable in permanent magnets, so that the magnets retain a strong field and are not demagnetized in response to external magnetic interactions.