What does coercivity mean?
Coercivity, also called coercive force, is a measure of how permanent a magnet is, or how much magnetic force is needed to reverse its magnetization. Coercivity is usually measured in units such as oersteds or amperes and abbreviated with the symbol Hc. Materials with high coercivity require strong magnetizing fields to be magnetized or demagnetized. Coercivity is therefore defined as the value of a magnetizing field required to return the magnet's magnetization to zero after it has been magnetized. Coercivity also varies with the composition and structure of the material and can be altered by cold working. Coercivity can also be measured using a magnetometer.