Many complex terms used when describing magnetism and permanent magnets, some of which prove confusing. Therefore, we’ve expanded on some of the most common terms, helping you to better understand your magnetic requirements.
This is a low permeability gap in the flux path of a magnetic circuit, which is non-magnetic and also often air. However, the gap may include other materials such as brass, aluminium or paint.
These are magnets which have a preferred direction of orientation, with their alignment defined during the manufacturing process in a strong magnetic field.
The B/H curve comes from plotting the value B (induction) against H (applied magnetic field). The curve outlines the qualities of the magnetic material.
BHmax (Maximum Energy Product)
This is the maximum energy product on the point of the B/H curve that has the highest strength. Reflected as MGO, or Mega Gauss Oersteds.
Exists when the flux path outside of the permanent magnet is kept within high permeability materials which contain the magnet circuit.
Coercive Force (HC)
Measured in Oersteds, coercive force reflects the resistance of a magnet to demagnetising forces once an opposing magnetic field is applied to remove the residual magnetism.
The temperature at which a magnet loses all its magnetic properties and is therefore not able to hold magnetism.
Also referred to as the B/H Curve, this is the second quadrant of the hysteresis loop. Generally used to describe the performance of magnetic characteristics in actual use.
Ferro magnetism is the basis for many electrical and electromagnetic devices ranging from the refrigerator magnet to motors and transformers. It is a physical phenomenon that allows certain materials to become permanent magnets. Iron, nickel and cobalt (and their alloys) fall into this category. Although, rare-earth magnets are a relatively new class of exceptionally strong ferromagnetic materials.
Flux is the magnetic entity which flows from one pole to the other in a magnetic circuit.
Simply, Gauss refers to the units of magnetic induction. Measured in Maxwell lines, CGS Units or Tesla.
Otherwise known as partial demagnetisation of the magnet. This occurs when the magnet has been exposed to extremely high or low temperatures, external fields, shock, vibration, or other factors. Such losses are only recoverable by re-magnetising.
The opposite of anisotropic magnets, isotropic magnets do not have a preferred direction of magnetic orientation. Therefore, they can be magnetised in any direction without the loss of magnetic properties.
Exists when a magnet is by itself with no return flux path due to high permeability material.
A magnet that retains its magnetism even after it is removed from a magnetic field. Therefore, the magnet remains “on” without the need for any outside field.
Permeance Coefficient (Pc)
Also referred to as the load-line. Permeance coefficient is the line on the demagnetisation curve that intersects the -B/H curve and the slope represents the operating point of the magnet.
The force required to pull a magnet free from a flat steel plate using a force perpendicular to the surface. This helps to determine the holding power of the magnet.
Calculated by dividing magnet motive force by magnetic flux, reluctance is a measure of the relative resistance of a material to the passage of flux.
The magnetic induction which remains in a magnetic circuit after the removal of an applied magnetising force.
The condition of a magnet where it has reached maximum value and an increase in magnetising force produces no further increase in the magnetic material.
A sintered magnet is compacted powder, then heat treated to achieve full density and orientation.
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