Keeper: A piece of soft iron that is placed on or between the poles of a magnet, decreasing the reluctance of the air gap and thereby reducing the flux leakage from the magnet.

Intrinsic Coercive force, Hci: Measured in Oersteds in the cgs system, this is a measure of the material’s inherent ability to resist demagnetization.

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Isotropic Magnet: A magnet material whose magnetic properties are the same in any direction, and which can therefore be magnetized in any direction without loss of magnetic characteristics.

Induction, B: The magnetic flux per unit area of a section normal to the direction of flux. Measured in Gauss, in the cgs system of units.

Irreversible Loss: Defined as the partial demagnetization of a magnet caused by external fields or other factors. These losses are only recoverable by remagnetization. Magnets can be stabilized to prevent the variation of performance caused by irreversible losses

Hysteresis Loop: A closed curve obtained for a material by plotting corresponding values of magnetic induction, B, ( on the abscissa ) against magnetizing force, H (on the ordinate).