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Magnetic Hysteresis Curve

Standard magnetic properties are indicated with the magnetic hysteresis curve shown in the following graph.
Place the magnetic field and gradually intensity the field from zero position in the figure. Flux density in the field suddenly increases at first ; subsequently, the increasing rate of flux density reduces and, finally, flux density increases only by the intensity added to the field.
This condition is called "saturation", which is point(a) in the Fig. 1.
When reducing intensity of the field from the saturation state, flux density decreases along the curve a→b, that is, hysteresis occurs.
When setting the intensity of the field to zero, induction of ob remains.
This value is referred to as Br (residual induction).
Moreover, when the intensity of the field in the opposite direction is increased, flux density gradually decreases to zero at point c in the Fig. 1.
The intensity of the opposite direction field (the value oc in the Fig. 1) is called "Hc" (coercive force).
Furthermore, when the intensity of the field is increased, flux density increases in the opposite direction along the curve c→d, subsequently indicating the cycle d→e→f→a→b.
This curve is called the "magnetic hysteresis curve".
The properties of materials used for magnets are generally expressed in the second quadrant including the curve b→c.
This partial curve is called the "demagnetization curve".
The unit for the intensity of field H is referred to as Oersted and the unit for induction B as Gauss. Oersted and Gauss are the CGS electromagnetc unit.
Expressing them in SI unit, they are respectively shown as ampere/meter (A/m) and Tesla(T), presenting the following relations

1 Gauss = 10-4 T
1 Oersted = 79.58 A/m