Glossary of Magnet Terms
Anisotropic (oriented) – The material has a preferred direction of magnetic orientation.
Coercive force – The demagnetizing force, measured in Oersted, necessary to reduce observed induction, B to zero after the magnet has previously been brought to saturation.
Curie temperature – The temperature at which the parallel alignment of elementary magnetic moments completely disappears, and the materials is no longer able to hold magnetization.
Gauss – Unit of measure of magnetic induction, B, or flux density in the CGS system.
Gaussmeter – An instrument used to measure the instantaneous value of magnetic induction, B.
Flux The condition existing in a medium subjected to a magnetizing force. This quantity is characterized by the fact that an electromotive force is induced in a conductor surrounding the flux at any time the flux changes in magnitude. The unit of flux in the GCS system is Maxwell. One Maxwell equals one volt x seconds.
Induction – The magnetic flux per unit area of a section normal to the direction of flux. The unit of induction is Gauss in the GCS system.
Irreversible Loss – The partial demagnetization of a magnet caused by external fields or other factors. These losses are only recoverable by re-magnetization. Magnets can be stabilized to prevent the variation of performance caused by irreversible losses.
Intrinsic Coercive Force, Hci – Oersted measurement of the material’s inherent ability to resist self-demagnetization.
Isotropic (non-oriented) – The material has no preferred direction of magnetic orientation, which allows magnetization in any direction.
Magnetizing Force – The magnetomotive force per unit length at any point in a magnetic circuit. The unit of the magnetizing force is Oersted in the GCS system.
Maximum Energy Product (BH)max – There is a point at the Hysteresis Loop at which the product of magnetizing force H and induction B reaches a maximum. The maximum value is called the Maximum Energy Product. At this point, the volume of magnet material required to project a given energy into its surrounding is a minimum. This parameter is generally used to describe how “strong” this permanent magnet material is. Its unit is Gauss Oersted. One MGOe means 1,000,000 Gauss Oersted.
Magnetic Induction – B -Flux per unit area of a section normal to the direction of the magnetic path. Measured in gauss.
Maximum Operating Temperature – The maximum temperature of exposure that a magnet can forego without significant long-range instability or structural changes.
North Pole – That magnetic pole which attracts the geographic North Pole.
Oersted, Oe – A unit of magnetizing force in GCS system. 1 Oersted equals 79.58 A/m in SI system.
Permeability, Recoil – The Average slope of the minor hysteresis loop.
Polymer-Bonding – Magnet powders are mixed with a polymer carrier matrix, such as epoxy. The magnets are formed in a certain shape, when the carrier is solidified.
Residual Induction, Br -Flux density – Measured in gauss, of a magnetic material after being fully magnetized in a closed circuit.
Rare Earths Magnets – Magnets made of elements with an atomic number from 57 to 71 plus 21 and 39. They are lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.
Remanance, Bd – The magnetic induction which remains in a magnetic circuit after the removal of an applied magnetizing force. If there is an air gap in the circuit, the remenance will be less than the residual induction, Br.
Reversible Temperature Coefficient – A measure of the reversible changes in flux caused by temperature variations.
Residual Induction – Br A value of induction at the point at Hysteresis Loop, at which Hysteresis loop crosses the B axis at zero magnetizing force. The Br represents the maximum magnetic flux density output of this material without an external magnetic field.
Saturation – A condition under which the induction of ferromagnetic material has reached its maximum value with the increase of applied magnetizing force. All elementary magnetic moments have become oriented in one direction at the saturation status.
Sintering – The bonding of powder compacts by the application of heat to enable one or more of several mechanisms of atom movement into the particle contact interfaces to occur; the mechanisms are: viscous flow, liquid phase solution-precipitation, surface diffusion, bulk diffusion, and evaporation-condensation. Densification is a usual result of sintering.
Surface Coatings – Unlike Samarium Cobalt, Alnico and ceramic materials, which are corrosion resistant, Neodymium Iron Boron magnets are susceptible to corrosion. Based upon the magnet application, following coatings can be chosen to apply on surfaces of Neodymium Iron Boron magnets – Zinc or Nickel.
