FERROMAGNETISM

Ferro-magnetism is very commonly used type of magnetism. Ferromagnetism is found on the Bar magnets, compass needles, and the coating on magnetic hard disks. It is a fine property of iron, cobalt, and compounds of these few other metals which includes nickel, chromium and magnesium. All these stated materials shows ferromagnetic properties because the spins of the electrons cancel out much less than in other materials. Groups of spinning electrons align readily with an external magnetic field, thus forming magnetic domains. This alignment is permanent so that the material becomes magnetized, & remains so, even when we remove the external field.

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Hysteresis loss

A disturbance in the alignment of the domains, referred as groups of atoms, of ferro-magnetic material give rise to energy to be expended in taking it through a cycle of magnetization. This energy acts as heat in the specimen and is known as the hysteresis loss. The amount of energy loss associated with hysteresis is proportional to the area of the hysteresis loop.The area of a hysteresis loop greatly depends on the type of material. The area, and thus the energy loss, is very bigger for hard materials than for soft type materials.

Diagram below shows typical hysteresis loops for:

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