What does coercivity mean?

Coercivity, or coercive field strength, is a measure of how permanent a magnet is, or the amount of magnetic force required to reverse its magnetization. Coercivity is usually measured in units such as oersted or amperes and abbreviated by 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 magnetization of the magnet to zero after it has been magnetized. Coercivity further varies with the composition and structure of the material, and can be altered by cold working. Coercivity can also be measured by using a magnetometer.