magnetization curve[‚mag·nəd·ə′zā·shən ‚kərv]
a graph, table, or formula that shows the dependence of the magnetization J or magnetic induction B on the magnetic-field intensity H. If the function J(H) is known, then the induction curve B(H) can be constructed for the same substance, since the simultaneous values of B, J, and H that refer to the same volume element of the substance are related by the equation B = H + 4∏J (in the centimeter-gram-second system of units) or B = μ0 (H + J) (in SI units, where μ0 is the magnetic constant).
The magnetization curves for magnetic materials depend not only on the physical properties of the materials and the external conditions but also on the sequence of passage through various magnetic states. In this connection, we consider several types of magnetization curves: (1) curves of initial magnetization (Figure
1), which are the sequences of values of J or B that a substance assumes as H increases monotonically from an initial state with B = H = J = 0 (in this case, H does not change direction); (2) cyclic magnetic-reversal curves (or static hysteresis loops), which are the functional forms of B(H) or J(H) that are obtained after repeated passage through a certain range of values of H in the forward and reverse directions (Figure 2); and (3) normal magnetization (or commutation) curves, which are the loci of the tips of the symmetric loops of magnetic reversal (Figure 2).
Magnetization curves enable us to determine the characteristics of magnetic materials, for example, residual magnetization, coercive force Hc, and magnetic permeability. These characteristics are used in design calculations for the magnetic circuits of electromagnets, magnetic starters, relays, and other electrotechnical devices and instruments.
REFERENCESKifer, 1.1. Ispytaniia ferromagnitnykh materialov, 3rd ed. Moscow, 1969.
Bozorth, R. Ferromagnetizm. Moscow, 1956. (Translated from English.)