Air Gap  
The distance between one pole of the magnet and the other magnetic material.  The air gap is non-magnetic, usually air, but can be a non-magnetic material.

Materials that have an orientation that is aligned in a preferred direction.  Anisotropic magnets have their alignment defined during the manufacturing process in a strong magnetic field.   Once the preferred direction is determined, this direction 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.

BHmax (Maximum Energy Product)
The maximum energy product on the point of the B/H curve that has the highest strength.  This is reflected as mgo, or mega gauss oersteds.  This maximum strength is how the material grade is determined, i.e. N35, N42, N48, etc.

This is also known as the Residual Flux Density, and is the point on the hysteresis loop that crosses the B axis at zero magnetizing force.  Once a magnet is saturated, the magnetic field is removed resulting in the maximum flux output of the magnet.  

An abbreviation system of units utilizing centimeters, grams, and seconds.

Coercive Force (Hc)
The resistance of a magnet to demagnetizing forces once an opposing magnetic field is applied to remove the residual magnetism.

Curie Temperature
The temperature at which a magnet loses all of its magnetic properties.

Demagnetization Curve
The second quadrant of the hysteresis loop, and also referred to as the B/H Curve.  Demagnetization Curves can be found on our Material pages.  

Demagnetization Force
A force that pushes the magnet pushes the magnet to demagnetize slightly or completely.  These forces could include a magnetizing force in the opposite directly, shock, temperature, and vibration.

Dimensional Tolerance
The total amount a dimension may vary between the upper and lower limits.  Tolerances are used to control the amount of variation in a manufactured part.

Ferromagnetic Material
Ferromagnetic materials can carry magnetic flux when against a magnet, and is usually made of steel.   These materials can act like a magnet until the magnetic material is removed.

The magnetic entity which flows from one pole to the other in a magnetic circuit.  

Unit of magnetic induction, B.  10,000 gauss equals 1 Tesla

Hysteresis Loop
The Full 4-quadrant graph showing the relationship of the induction of a magnetic material to an applied magnetic field.  The first quadrant of the loop is the magnetization curve, while the second quadrant of the loop is the Demagnetization Curve.

Induction (B)
The concentration of flux over a given area measured in gauss or tesla.  

Intrinsic Coercive Force (Hci)
The resistance of a magnet material to demagnetization.   It is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to zero after magnetizing to saturation.

Irreversible Losses
Partial demagnetization of the magnet, caused by exposure to high or low temperatures, external fields, shock, vibration, or other factors.  The losses are only recoverable by remagnetizing.  

Isotropic Material
A material that can be magnetized along any axis or direction.  Opposite of anisotropic magnets.

One kilogauss = 1,000 gauss.

Load Line
The line drawn from the origin of the demagnetization curve with the slope of the B/H.  The intersection represents the operating point of the magnet.

A piece of iron that has its component atoms oriented within the material that the material exhibits properties of magnetism.  This allows the material to attract other materials containing iron, or align itself with an external magnetic field.

Magnetic Assembly
A combination of magnetic and/or non-magnetic materials that includes the permanent magnet to generate flux.   This assembly of specific materials is designed to provide a defined magnetic solution.

Magnetic Circuit
One or more closed loop paths containing magnetic flux.  The magnetic circuit is equivalent to an electrical circuit.

Material Grade
Magnets are graded according to strength, and as a rule, the higher the number, the “stronger” the magnet.  For example, neodymium magnets (NdFeB) have grades from N35 to N55.  The energy product of a magnet is specified in units of gauss oersted.  Choice of a magnetic grade for a specific application will require consideration of magnetic field required, cost, size, operating temperature, coatings and interaction with other materials.  

Maximum Energy Product (BHmax)
The maximum energy product on the point of the B/H curve that has the highest strength.  This is reflected as mgo, or mega gauss oersteds.  This maximum strength is how the material grade is determined, i.e. N35, N42, N48, etc.

The unit of magnetic flux in the centimeter-gram-second (cgs) system.  One Maxwell is one line of magnetic flux.  

Mega (million) gauss oersteds is a unit of measurement typically used in stating the maximum energy product for a given material.

North Pole
The pole of a magnet which points to the north magnetic pole of the earth.  All magnets have a north and south pole.

The centimeter-gram-second (C.G.S) unit of magnetic field strength.

Open Circuit
An open circuit exists when a magnet is by itself with no return flux path due to high permeability material.

In an anisotropic magnet, the direction that the magnetic field flows.  Anisotropic magnets have their direction of orientation determined during the manufacturing process and can only be magnetized in that specific direction.

A form of magnetism where certain materials are attracted by an externally applied magnetic field and form internal induced magnetic fields in the direction of the applied magnetic field.

Permanent Magnet
A magnet that retains its magnetism even after it is removed from a magnetic field.  Unlike an electromagnet that requires current to achieve a magnetic field, a permanent magnet remains “on” without the need for any outside field.

Permeance (P)
A measure with which flux passes through a given material or space.  It is the reciprocal of the reluctance, R, measured in maxwells per gilbert.

Permeance Coefficient (Pc)
Also called the load-line, B/H or operating slope.  Permeance coefficients can be found as the line on the demagnetization curve where a given magnet operates, and depends upon both the shape and surroundings of the magnet.  This number defines how hard it is for the field lines to go from the north pole to the south pole of the magnet.

Plating and/or Coating
The protective coating on a magnet.  Neodymium magnets require a coating to protect from corrosion since their material make up is largely iron.  Depending upon the application and environment, the correct coating choice is as important as the correct selection of the magnetic material.    

The north and south pole of the magnet.  

Pull Force
The force required to pull a magnet free from a flat steel plate using a force perpendicular to the surface.  This will determine the holding power of the magnet.

A measure of the relative resistance of a material to the passage of flux, which is calculated by dividing magneto motive force by magnetic flux.  

Return Path
Conduction elements in a magnetic circuit that provide a low reluctance path for the magnetic flux.

The condition of a magnet where an increase in magnetizing force produces no further increase in the magnetic material.   When this condition is met, all of the magnetic moments have the same alignment.  A magnet should always be magnetized to saturation.

A sintered magnet is compacted powder which is then heat treated to achieve full density and orientation.

South Pole
The pole of a magnet which points to the south magnetic pole of the earth.  All magnets have a north and south pole.

The process of exposing a fully saturated magnet or magnetic assembly to an elevated temperature or external magnetic field to demagnetized it to a predetermined level.  Once stabilized through this process, the magnet should not experience any future degradation when exposed to that level of demagnetizing influence again, or better known as preventing irreversible losses during.

Surface Field
The magnetic field strength at the surface of the magnet as measured by a gauss meter.  

Temperature Coefficient
A factor that is used to calculate the decrease in magnetic flux with an increase in operating temperature.  This loss is recovered when the operating temperature is decreased.  Understanding temperature requirements in an application will allow for the correct selection of magnetic material.

One (1) Tesla equals 10,000 gauss.

The practical unit of magnetic flux.  It is the amount of the magnetic flux which, when linked at a uniform rate with a single-turn electric current during an interval of 1 second, will induce in this circuit an electromotive of force of 1 volt.