Glossary of Terms

The GLOSSARY

Air Gap –The space or distance between a magnet or magnetically receptive surface. It may consist of air but can be created by other materials such as styrene, cardboard or a non-ferrous metal like aluminum.

Alnico –Magnets are made primarily with aluminum, nickel, cobalt, copper, iron and occasionally titanium. Alnico magnets can be cast or sintered, and are very temperature stable, however the material is very hard and brittle, not naturally lending itself to conventional machining.

Anisotropic (oriented) –The material has a preferred direction of magnetic orientation assigned during the magnetization process. Once the direction is determined, it cannot be changed.

B/H Curve –The curve produced from plotting the value B (induction) against H (applied magnetic field). The curve will describe the qualities of the magnetic material when a magnet is magnetized and then when it is demagnetized.

Br, Residual Induction –The magnetic induction corresponding to zero magnetizing force in a magnetic material; measured in gauss.

Ceramic –Magnets are composed of strontium carbonate and iron oxide. Ceramic magnets are less expensive than alnico and neodymium magnets, with a lower temperature threshold than alnico, but greater than neodymium. Lower grade ceramic magnets can be non-oriented. Learn more about ceramic magnets.

Coercive Force, Hc –The amount of force, as measured by Oersteds, required to reduce the magnetization of a permanent magnet to zero. Some types of magnets, ceramic for example, are more easily demagnetized than others.

Curie Temperature –Temperature above which a material loses its magnetic properties.

Demagnetization Force –A force, which is the opposite direction of the field of a magnet, which removes the flux of a magnet after it has been fully magnetized.

Ferrite –A magnet consisting of iron oxide and strontium.

Ferrous Metal –The term "ferrous" is derived from the Latin word meaning "containing iron". Ferrous metals are often magnetic, but not exclusively.

Flux –Describes the flow of the magnetic field of an object or magnetically receptive object.

Gauss –Unit of measure of magnetic induction, B, or flux density in the C.G.S.

Gaussmeter –An instrument that indicates the strength of a magnetic field at any point directly in gauss.

Hysteresis Loop - A closed curve obtained for a material. Obtained by plotting corresponding values of magnetic induction, B, for ordinates and magnetizing force, H, for abscissa when the material is passing through a complete cycle between definite limits of either magnetizing force, H, or magnetic induction, B. This data is usually plotted to rectangular coordinates.

Intrinsic Coercive Force, Hci –Oersted measurement of a material’s inherent ability to resist demagnetization.

Isotropic (non-oriented) –Material that has no preferred direction of magnetic orientation, which allows magnetization in any direction.

Mega Gauss-Oersteds (MGOe) –The stored energy in a magnet, called magnet performance or magnetic energy product, is typically measured in units of mega gauss-oersteds.

Magnet –A magnet is an object of certain materials, either natural or manufactured, that attracts ferrous materials with a magnetic field. All magnets have at least two poles – north and south – and will retain their poles, even if broken into smaller pieces. It is not possible to end up with a single-pole magnet (also known as a monopole).

Magnetic Assembly –A composition of magnetic and non-magnetic materials designed to focus or direct the magnetic flux which increases its strength.

Magnetic Field Strength (magnetizing or demagnetizing force) –The measure of the vector magnetic quantity that determines the ability of an electric current, or a magnetic body, to induce a magnetic field at a given point; measured in oersteds.

Magnetic Induction, B –Flux per unit area of a section normal to the direction of the magnetic path. Measured in gauss.

Magnetic Polarity –The north and south poles of a magnet where the flux lines are concentrated.

Magnetic Saturation –The maximum amount of energy that can be absorbed by a magnetic material to fully “charge” a magnet.

Material Grade –The ranking by which magnetic strength is determined. As a general rule, a higher number equates to a stronger magnet. For example, neodymium magnets have grades from N35 to N52. Magnetic grade factors into application, cost, size, operating temperature, and more.

Max Force –Maximum strength of a magnet when attracted to .5” steel. Also known as pull force or pull strength. See Measuring Pull Strength for more details.

Maximum Energy Product, BHmax –The maximum product of (BdHd) which can be obtained on the demagnetization curve.

Maximum Operating Temperature –The maximum temperature of exposure that a magnet can forego without significant long-range instability or structural changes.

Neodymium (Nd-Fe-B) –One of the “rare earth magnets,” neodymium magnets are composed of neodymium, iron, boron, and transition metals. Despite their small size, these magnets are incredibly strong and are high-energy. Neodymium magnets should be handled with particular care to avoid injury.

North Pole –That magnetic pole which attracts the geographic South Pole, where flux originates from.

Oersted –The unit of measurement for the auxiliary magnetic field, H in the centimeter – gram – second system of units (CGS). It is equivalent to 1 dyne per maxwell.

Orientation –In an anisotropic magnet, the orientation is the direction that the magnetic field flows. Orientation is determined during the manufacturing process and is magnetized in one direction.

Permanent Magnet –A magnet that retains its magnetic properties in the absence of an inducing field or current.

Plating –Also known as coating, this is the process of covering the magnetic material to help prevent corrosion of the iron-based materials.

Pull Force –Also known as pull strength or Max Force, pull force is the minimum required force to separate a magnet from a ferrous, metal surface to which it has attracted. The holding power of a magnet is determined by measuring pull force. Master Magnetics traditionally tests pull force on magnetic assemblies only.

Rare Earth Magnets –Neodymium (Nd-Fe-B) and samarium cobalt (SmCo) are the strongest permanent magnets available and have significantly higher performance than ferrite (ceramic) and alnico magnets.

Residual Induction, Br –Flux density, measured in gauss, of a magnetic material after being fully magnetized in a closed circuit.

Samarium Cobalt (SmCo) –A second type of rare earth magnet, it is composed of samarium, cobalt and iron. Samarium cobalt magnets have high resistance to demagnetization, good temperature stability and are high-energy.

Shear Force –The force on a magnet when it is placed in a perpendicular position to the ground. A magnet’s shear force holding power is usually about half of its strength in a horizontal position.

South Pole –The magnetic pole that attracts to the geographic North Pole where flux from the North Pole terminates.