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Ferrite Magnetism

May 16th Fact-of-the-Day

Sintered ferrite contains crystals that generally range from 10 to 20 mm in size. Those crystals contain tiny, saturated, molecular magnets known as Weiss domains. Magnetic coupling between Weiss domains causes their magnetic moments to align with each other. When an electric current flows through a coil wound around ferrite an electromagnetic field is produced around the coil. That field tends to force the tiny Weiss domain molecular magnets to align with it, but before re-alignment can occur, the energy-barrier of the magnetic coupling between Weiss domains must be overcome. The time required to overcome that energy barrier makes ferrite magnetization always lag behind electromagnetic field changes from the coil. If ferrite magnetization is plotted against coil electromagnetic field strength, the retardation causes the plot to loop. That loop is called a hysteresis (from Greek hysterein, 'to be late') loop. ©2005 Martek International All rights reserved.


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