Dictionary of technical terms

⎯ A

ALNICO

Abbreviation for Aluminium Nickel Cobalt which refers to one of the oldest families of permanent magnets still widely used today.

Magnetisation

Spontaneous magnetic property of certain materials when subjected to the action of an external magnetic field. This property expresses the capacity of a given material to spontaneously generate its own magnetic field under the action of an external magnetic field. This property is similar to a magnetic field amplification phenomenon.

⎯ B

B

Abbreviation, generally refers to a magnetic induction field.

Br

Abbreviation, generally refers to the remanent induction of a magnet.

⎯ C

Magnetic calibration

The process of partial and controlled demagnetisation of the magnet, in order to adjust the level of magnetic induction flux or magnetic induction field it generates in a given magnetic circuit.

Coercive field

Expresses the ability of a magnet to resist demagnetisation by external means. Generally refers to the coercive induction field for ALNICO magnets or magnetic steels. Refers to the intrinsic coercive (or magnetising) field in more recent magnets such as hard ferrites and rare earth magnets.

Coercive induction field

A demagnetising field, which it is necessary to apply within a magnet to achieve the cancellation of all magnetic induction within that magnet. In this situation, the magnet is not completely demagnetised but the demagnetising field applied is exactly opposite to the magnetic field generated by the magnetisation of the magnet.

Intrinsic coercive field

A demagnetising field, which it is necessary to apply within a magnet in order to obtain the cancellation of any magnetisation within that magnet. In this situation, the magnet is almost completely demagnetised. The magnetic induction field inside the magnet is opposite to its initial magnetisation. This is an extreme situation, to which the magnet should never be subjected, as it loses its permanent magnetisation.

Demagnetising field

A magnetic field applied to a magnet when the direction of the field is opposite to that of the magnetisation in the magnet.

Magnetic field

A mathematical concept derived from the looped flow of an electric current. It is the excitation at the origin of all magnetic phenomena and is indispensable for the establishment of a magnetisation or a magnetic induction. It can be established in all existing materials.

Magnetic induction field

Generally designated by the letter B, corresponds to the effect of a magnetisation or a magnetic field inside a given material.

Magnetic circuit

A set of magnets, coils through which currents flow, and soft ferromagnetic components. The function of the magnetic circuit is to generate a magnetic induction field, amplify it and conduct it to the air gap where it is used.

⎯ E

Air gap

A region of a magnetic circuit, usually filled with air to accommodate the sensing elements intended to use the magnetic induction field produced.

⎯ F

Ferromagnetism

This is the property of being able to generate a magnetization that is added to the magnetic field that gave rise to it. This property is similar to a magnetic field amplification phenomenon.

Magnetic induction flux

Often shortened to “magnetic flux”. Is defined as the product of the magnetic induction field and the value of the surface through which it passes. It can be interpreted as the equivalent of an electric current in an electric circuit or a flow in a hydraulic circuit. This is a very important concept, especially in electrical machines where i is directly related to the voltage of a generator or the torque of a motor.

⎯ H

H

Abbreviation, usually refers to a magnetic field.

Hc

Abbreviation, refers to the coercive induction field (Anglo Saxon).

HcB

Abbreviation, refers to the coercive induction field (France).

Hcj

Abbreviation, refers to the intrinsic coercive field or magnetization field.

Remanent induction (or magnetisation)

Corresponds to the maximum magnetic induction field that a magnet can deliver when it is not subjected to any demagnetisation stress (corresponds to the theoretical situation where the north and south poles of the same magnet are in contact. In practice the actual magnetic induction field delivered by a magnet is always lower than this value.

⎯ J

J

Abbreviation, refers to magnetisation.

Jr

Abbreviation, refers to the remanent magnetisation of a magnet.

µr

Abbreviation, refers to the magnetic recoil permeability.

⎯ M

Ferromagnetic material

A material that exhibits ferromagnetic properties. There are 2 main subfamilies of products: hard ferromagnetic materials and soft ferromagnetic materials. Common ferromagnetic materials are iron, nickel, cobalt, chromium dioxide, dysprosium, gadolinium, etc.

Hard ferromagnetic materials

Materials that can retain a remanent induction beyond the application of the magnetic field that gave rise to it. These are permanent magnets.

Soft ferromagnetic materials

Materials that generate magnetisation only when an external magnetic field is applied. In contrast to magnets, the remanent induction and coercive field of these materials is very low. These materials are used only to amplify the magnetic field to which they are subjected. By analogy with electricity, they are also said to conduct the magnetic induction field.

⎯ N

Magnetic grade

From a product family, by modifying the manufacturing process steps and/or by adding specific elements to the basic composition, it is possible to generate a set of grades of the same material. The grades differ from each other in their magnetic properties and in the balance between remanent induction and coercive field values.

⎯ P

Recoil magnetic permeability

This quantity expresses the gain of the reversible variation of the magnetic induction field generated by the magnet, compared to the variation of the demagnetising field applied in the magnet. It is in fact the average slope of the recoil lines of the B(H) hysteresis cycle

Polarity

A phenomenon resulting from the magnetisation of a magnet. This magnetisation generates a magnetic induction field which passes through the magnet and all the surrounding space. By convention, the magnetic field exits the magnet at its north pole and returns to the magnet at its south pole.

⎯ T

Curie temperature

Temperature above which the thermal agitation within a material is such that no magnetisation can be observed. For all magnets, passing this temperature is an effective means of achieving near perfect demagnetisation.

Tc

Abbreviation for the Curie temperature of a material.