Aging, Magnetic

a change in the magnetic properties of a ferromagnetic material over time. Magnetic aging can result from changes in the domain structure of the ferromagnetic’s crystal structure (irreversible magnetic aging).

Reversible magnetic aging is caused by a rearrangement of the domain structure (seeDOMAINS) under the action of external factors, such as magnetic fields, temperature fluctuations, or mechanical vibrations. This type of aging is exhibited most clearly in ferromagnetics with residual magnetism. Remagnetization removes the effects of reversible magnetic aging and restores the original magnetization of the ferromagnetic specimen.

Irreversible magnetic aging occurs when the crystal structure of a ferromagnetic material undergoes a transition from a metasta-ble state to a state that is closer to equilibrium. This type of aging occurs whether or not the specimen is demagnetized or has residual magnetism. An increase in temperature accelerates irreversible magnetic aging.

The magnetic stability of ferromagnetic products can be improved by subjecting the products to artificial aging. The crystal structure can be stabilized by holding the article at an elevated temperature. Partial demagnetization by an alternating magnetic field is the simplest method of stabilizing the magnetic domain structure of products used in a state of residual magnetism. The best stability of magnetization is achieved when the demagnetizing action used in artificial aging is the same as the demagnetizing action to which the product is subjected during its use.