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.

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.

Knee of the Demagnetization Curve: The point at which the B-H curve ceases to be linear. All magnet materials, even if their second quadrantcurves are straight line at room temperature, develop a knee at some temperature. Alnico 5 exhibits a knee at room temperature. If the operating point of a magnet falls below the knee, small changes in H produce large changes in B, and the magnet will not be able to recover its original flux output without remagnetization.

Leakage Flux: That portion of the magnetic flux that is lost through leakage in the magnetic circuit due to saturation or air-gaps, and is therefore unable to be used

Length of Air-Gap, Lg: The Length of the path of the central flux line in the air-gap
.
Load Line: A line drawn from the origin of the Demagnetization Curve with a slope of B/H, the intersection of which with the B-H curve represents the operating point of the magnet. Also see Permeance Coeffcient.

Magnetic Circuit: An assembly consisting of some or all of the following: permanent magnets, ferromagnetic conduction elements, air gaps,
electrical currents.

Magnetic Flux, Ø: The total magnetic induction over a given area. When the magnetic induction, B, is uniformly disributed over an area A, Ø=BA. The general equation is Ø=B. dA.

Magnetizing Force, H: The magnetomotive force per unit length at any point in a magnetic circuits. Measured in oersteds in the cgs system.

Magnetomotive Force, F: Analogous to voltage in electrical circuits, this is the magnetic potential difference between any two points.

Maximum Energy Product, BHmax: The point on the Demagnetization Curve where the product of B and H is a maximum and the required volume of magnet material required to project a given energy into its surroundings is a minimum. Measured in Mega Gauss Oersteds, MGOe.