What is a hysteresis loop in magnetism?
A four quadrant graph showing the magnetizing force relative to the resulting magnetization of a permanent magnet material as it is successively magnetized to its saturation point, then demagnetized, magnetized in the reverse polar direction and finally re-magnetized.
When the cycles are complete, this four quadrant graph will be a closed loop that illustrates the magnetic properties of the magnetic material being tested. Magnetically hard materials have a larger area inside the loop, which indicates the amount of magnetic energy. Magnetically soft materials lose their magnetism when the magnetizing field is removed and therefore have very small areas inside the loop. The second quadrant of the four quadrants (+X and -Y) is the most important of the four curves and is called the demagnetization curve.