Ndfeb magnet Terminology

There are some magnet termimology's glossary for ndfeb magnet,neodymium magnet,rare earth magnet,magnetics,permanent magnets,it can help you understanding magnetics.

Magnetic Circuit - Consists of all elements, including air gaps and non-magnetic materials that the magnetic flux from a magnet travels on, starting from the north pole of the magnet to the south pole
Magnetic Field Strength (H) - Magnetizing or demagnetizing force, is 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 Flux - Is a contrived but measurable concept that has evolved in an attempt to describe the “flow” of a magnetic field.  When the magnetic induction, B, is uniformly distributed and is normal to the area, A, the flux, Ø = BA.

Magnetic Flux Density - Lines of flux per unit area, usually measured in Gauss (C.G.S.). One line of flux per square centimeter is one Maxwell.

Magnetic Induction (B) - The magnetic field induced by a field strength, H, at a given point. It is the vector sum, at each point within the substance, of the magnetic field strength and the resultant intrinsic induction. Magnetic induction is the flux per unit area normal to the direction of the magnetic path.

Magnetic Line of Force - An imaginary line in a magnetic field, which, at every point, has the direction of the magnetic flux at that point.

Magnetic Pole - An area where the lines of flux are concentrated.

Magnetomotive Force (F or mmf) - The magnetic potential difference between any two points. Analogous to voltage in electrical circuits. That which tends to produce a magnetic field. Commonly produced by a current flowing through a coil of wire. Measured in Gilberts (C.G.S.) or Ampere Turns (S.I.).

Material Grade - Neodymium (NdFeB) magnets are graded by the magnetic material from which they are manufactured.  Generally speaking, the higher the grade of material, the stronger the magnet.  Neodymium magnets currently range in grade from N27 to N52.  The theoretical limit for Neodymium magnets is grade N64.  The grade of most of our stock magnets is N42 because we feel that N42 provides the optimal balance between strength and cost.  We also stock a wide range of sizes in grade N52 for customers who need the strongest permanent magnets available.

Maximum Energy Product (BHmax) - The magnetic field strength at the point of maximum energy product of a magnetic material.  The field strength of fully saturated magnetic material measured in Mega Gauss Oersteds, MGOe. 

Maximum Operating Temperature (Tmax) - Also known as maximum service temperature, is the temperature at which the magnet may be exposed to continuously with no significant long-range instability or structural changes.

Maxwell - Unit of magnetic flux in the C.G.S. electromagnetic system. One maxwell is one line of magnetic flux.

Magnetization Curve - The first quadrant portion of the hysteresis loop (B/H) Curve for a magnetic material.

Magnetizing Force (H) - The magnetomotive force per unit of magnet length, measured in Oersteds (C.G.S.) or ampere-turns per meter (S.I). Maxwell - The C.G.S. unit for total magnetic flux, measured in flux lines per square centimeter.

MGOe - Mega (million) Gauss Oersteds. Unit of measure typically used in stating the maximum energy product for a given material. See Maximum Energy Product.

North Pole - The north pole of a magnet is the one attracted to the magnetic north pole of the earth. This north-seeking pole is identified by the letter N. By accepted convention, the lines of flux travel from the north pole to the south pole.

Oersted (Oe) - The C.G.S. unit for magnetizing force. The English system equivalent is Ampere Turns per Inch (1 Oersted equals 79.58 A/m). The S.I. unit is Ampere Turns per Meter.

Orientation - Used to describe the direction of magnetization of a material. Orientation Direction - The direction in which an anisotropic magnet should be magnetized in order to achieve optimum magnetic properties.

Paramagnetic Materials - Materials that are not attracted to magnetic fields (wood, plastic, aluminum, etc.). A material having a permeability slightly greater than 1.

Permanent Magnet – A magnet that retains its magnetism after it is removed from a magnetic field. A permanent magnet is "always on". Neodymium magnets are permanent magnets.

Permeance (P) - A measure of relative ease with which flux passes through a given material or space. It is calculated by dividing magnetic flux by magnetomotive force. Permeance is the reciprocal of reluctance.

Permeance Coefficient (Pc) - Also called the load-line, B/H or "operating slope" of a magnet, this is the line on the Demagnetization Curve where a given magnet operates. The value depends on both the shape of the magnet, and it's surrounding environment (some would say, how it's used in a circuit). In practical terms, it's a number that define how hard it is for the field lines to go from the north pole to the south pole of a magnet. A tall cylindrical magnet will have a high Pc, while a short, thin disc will have a low Pc.

Permeability (µ) - The ratio of the magnetic induction of a material to the magnetizing force producing it (B/H).  The magnetic permeability of a vacuum (µo) is 4π×10-7 N/Amp2.

Pole - An area where the lines of magnetic flux are concentrated.

Plating/Coating - Most neodymium magnets are plated or coated in order to protect the magnet material from corrosion.  Neodymium magnets are mostly composed of neodymium, iron, and boron.  The iron in the magnet will rust if it is not sealed from the environment by some sort of plating or coating.  Most of the neodymium magnets that we stock are triple plated in nickel-copper-nickel, but some are plated in gold, silver, or black nickel, while others are coated in epoxy, plastic or rubber.

Polarity - The characteristic of a particular pole at a particular location of a permanent magnet. Differentiates the North from the South Pole.

Pull Force - The force required to pull a magnet free from a flat steel plate using force perpendicular to the surface. The limit of the holding power of a magnet.  The pull force listed is actual data acquired by testing using our state-of-the-art force test stand.  A comprehensive table of the pull force for all of our stock magnets is available here:  Pull Force Table.
We test for two different values of pull force using two different setups. Read more about these two pull forces here.

Rare Earth – Commonly used to describe high energy magnet material such as NdFeB (Neodymium-Iron-Boron) and SmCo (Samarium-Cobalt).

Relative Permeability - The ratio of permeability of a medium to that of a vacuum. In the C.G.S. system, the permeability is equal to 1 in a vacuum by definition. The permeability of air is also for all practical purposes equal to 1 in the C.G.S. system.

Reluctance (R)- A measure of the relative resistance of a material to the passage of flux. It is calculated by dividing magnetomotive force by magnetic flux. Reluctance is the reciprocal of permeance.

Remanence, (Bd) - The magnetic induction that remains in a magnetic circuit after the removal of an applied magnetizing force.

Residual Flux Density (Brmax) - Also called "Residual Induction".  It is the magnetic induction remaining in a saturated magnetic material after the magnetizing field has been removed.  This is the point at which the hysteresis loop crosses the B axis at zero magnetizing force, and represents the maximum flux output from the given magnet material.  By definition, this point occurs at zero air gap, and therefore cannot be seen in practical use of magnet materials.

Residual Induction (Brmax) - Also called "Residual Flux Density".  It is the magnetic induction remaining in a saturated magnetic material after the magnetizing field has been removed.  This is the point at which the hysteresis loop crosses the B axis at zero magnetizing force, and represents the maximum flux output from the given magnet material.  By definition, this point occurs at zero air gap, and therefore cannot be seen in practical use of magnet materials.

Return Path - Conduction elements in a magnetic circuit which provide a low reluctance path for the magnetic flux. Reversible Temperature Coefficient: A measure of the reversible changes in flux caused by temperature variations.

Saturation - The state where an increase in magnetizing force produces no further increase in magnetic induction in a magnetic material.

Shunt - A soft iron piece temporarily added between the pole of a magnetic circuit to protect it from demagnetizing influences. Also called a keeper. Not needed for Neodymium and other modern magnets.

South Pole - The south pole of a magnet is the one attracted to the south pole of the earth. This south-seeking pole is identified by the letter S. By accepted convention, the lines of flux travel from the north pole to the south pole.

Stabilization - The process of exposing a magnet or a magnetic assembly to elevated temperatures or external magnetic fields to demagnetize it to a predetermined level. Once done the magnet will suffer no future degradation when exposed to that level of demagnetizing influence.

Surface Field (Surface Gauss) - The magnetic field strength at the surface of the magnet as measured by a Gauss meter.  A comprehensive table of the surface field for all of our stock magnets is available here: