Glossary of Magnetic Terminology

Air Gap: The external distance from one pole of the magnet to the other pole through the air, or another non-magnetic material.

Anisotropic: Materials that have a preferred direction of magnetic orientation. These materials are typically manufactured in the influence of strong magnetic fields and can only be magnetized through the preferred axis.

BH max: Also known as maximum energy product, this is the magnetic field of strength at the point of maximum energy product of a magnetic material. This is the maximum product of BdHd which can be obtained on the demagnetization curve.

Br max: This is also known as residual flux density or residual induction. This is The magnetic flux density at which the magnetizing force is zero when the material is in a symmetrically and cyclically magnetized condition.

C.G.S: This an abbreviation for the "Centimeter, Grams, Second" system of measurement. The continued usage of CGS units is most prevalent in magnetism. This is also called gaussian units.

Coercive force: The opposing magnetic intensity that must be applied to a magnetized material to remove the residual magnetism.

Curie Temperature: The point in time where a material's permanent magnetism changes to induced magnetism as a result of the change in temperature.

Demagnetization curve: Graph of magnetic induction B versus magnetic field H in a ferromagnetic material, as the magnetic field is reduced to 0 from its saturation value. This is also known as the B-H Curve.

Demagnetization Force: This is a magnetizing force that is typically in the opposite direction to the force used to magnetize it initially. Temperature, shock, and vibration can all be demagnetizing forces.

Dimensions: This is simply the physical size of a magnet including all platings or coatings.

Dimensional Tolerance: This is an allowance given a a permissible range in the nominal dimensions of a finished magnet. The purpose of a tolerance is to specify the allowed leeway for imperfections in manufacturing.

Electromagnet: This is a magnet with an iron core and a solenoid. The only time an electromagnet has a magnetic field is when current is flowing through the solenoid.

Ferromagnetic Material: A material that either is a source of magnetic flux or a conductor of magnetic flux.

Gauss Meter: An instrument used to measure C.G.S.(centimeters, grams, second measurement).

Gilbert: Unit of magnetomotive force, F, in the Gauss (C.G.S.) system.

Hysteresis Loop: When a ferromagnetic material is magnetized in one direction, it will not relax back to zero magnetization when the imposed magnetizing field is removed. It must be driven back to zero by a field in the opposite direction. If an alternating magnetic field is applied to the material, its magnetization will trace out a loop called a hysteresis loop.

Induction: Magnetic flux per unit area of a section normal to the direction of flux. This is measure in Gauss in the C.G.S. system.

Intrinsic Coercive Force: This figure indicates a materials' resistance to demagnetization. It is equal of the demagnetizing force which reduces the induction, Bi, in the material to zero after magnetizing to saturation; measured in oersteds.

Irreversible Losses: This is when a magnet becomes partially demagnetized as a result of high or low temperatures, vibration, shock, external fields, or other factors. The only way that these loses can be recovered is by remagnetization. Magnets can be stabilized against irreversible losses by partial demagnetization induced by temperature cycles or external magnetic fields.

Isotropic Material: (Opposive of Anisotropic Magnet) This is a material that can be magnetized along any axis or direction, meaning that it is magnetically unoriented.

Keeper: Also known as a shunt, this is a soft iron piece that is temporarily added between the poles of a magnetic circuit in order to protect it from becoming demagnetized. These are not needed for modern magnets such as Neodymium.