Anisotropic 

An anisotropic material has different properties in different directions. For example, wood which has a grain is stronger in some one direction than another. Like wood, neodymium magnets are also anisotropic. Even before it is magnetized, a neodymium magnet has a "preferred" magnetization direction. 

Neodymium magnets are made with a preferred magnetization direction which can not be changed. These materials are either manufactured in the influence of strong magnetic fields or pressed in a specific way, and can only be magnetized through the preferred axis. Sintered Neodymium (Iron Boron) and Samarium Cobalt magnets are anisotropic.

B/H Curve

The result of plotting the value of the magnetic field (H) that is applied against the resultant flux density (B) achieved. 

BHmax (Maximum Energy Product)

The Maximum Energy Product at the point on the B/H Curve that has the most strength, expressed in MGOe (MegaGaussOersteds) or in kJ/m^3. When describing the grade of a neodymium magnet, this number is commonly referred to as the "N" number, as in Grade N52 magnets.

B_rmax (Residual Induction) 

Also called "Residual Flux Density". 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.

Coercive field (H_cB)

The demagnetizing magnetic field, necessary to reduce the observed induction, B, to zero after the magnet has previously been brought to saturation.

Coercive field (H_cJ) 

The demagnetizing magnetic field, necessary to reduce the observed magnetic induction, J, to zero after the magnet has previously been brought to saturation.

Curie Temperature (T_c) 

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

Demagnetization Curve

The second quadrant of the hysteresis loop, generally describing the behavior of magnetic characteristics in actual use. Also known as the B-H Curve. 

Dimensions

The physical size of a magnet including any plating or coating.

Dimensional Tolerance

An allowance, given as a permissible range, in the nominal dimensions of a finished magnet. The purpose of a tolerance is to specify the allowed leeway for variations in manufacturing.

Hysteresis Loop

A plot of magnetizing force versus resultant polarisation (also called a J/H curve) or magnetizing field versus of the material as it is successively magnetized to saturation, demagnetized, magnetized in the opposite direction and finally remagnetized. With continued recycles, this plot will be a closed loop which completely describes the characteristics of the magnetic material. The size and shape of this "loop" is important for both hard and soft materials. The first quadrant of the loop (that is +X and +Y) is called the magnetization curve. It is of interest because it shows how much magnetizing force must be applied to saturate a magnet. The second quadrant (-X and +Y) is called the Demagnetization Curve.

Induction (B)

The magnetic flux per unit area of a section normal to the direction of flux. 

Intrinsic Coercive Field (H_ci)

Indicates a materials' resistance to demagnetization. It is equal to the demagnetizing field 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. These losses are only recoverable by remagnetization. Magnets can be stabilized against irreversible losses by partial demagnetization induced by temperature cycles or by external magnetic fields.

Isotropic Material

A material that can be magnetized along any axis or direction (a magnetically unoriented material). The opposite of Anisotropic Magnet. 

Magnet

A magnet is an object made of certain materials which creates a magnetic field. Every magnet has at least one north pole and one south pole. By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. This is an example of a magnetic dipole ("di" means two, thus two poles).

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 N35 to N52. 

Maximum Energy Product (BHmax) 

The magnetic field strength at the point of maximum energy product of a magnetic material. 

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. 

Magnetization Curve

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

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. 

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.

Temperature Coefficient

A factor that is used to calculate the decrease in magnetic flux corresponding to an increase in operating temperature. The loss in magnetic flux is recovered when the operating temperature is decreased.