Magnet glossary

Conversion of common units of magnetic quantity

Name of magnetic quantity

Si symbols and units

CGS symbols and units

Unit conversion

Magnetic flux

Φ

Weber (WB)

Φ

Maxwell (MX)

1Mx=10-8 Wb

Magnetic induction intensity

B

Tesla (T)

B

Gauss (GS)

1Gs=10-4 T

Magnetic field strength

H

A / M

H

Oer (OE)

1Oe=103/4p A/m

Magnetization

M

A / M 

M

Gauss (GS)

1Gs=103 A/m

Magnetic polarization intensity

J

Tesla (T)

four p M

Gauss (GS)

1Gs=10-4 T

Magnetic energy product

BH

3(J/m3)

BH

Goe

1MGOe=102/4p kJ/m3

Vacuum permeability

 

4p•10-7H/m

one

Anisotropy – Materials with “preferred” magnetization direction. These materials usually have the magnetization direction at the time of manufacture and will not be changed by other strong magnetic fields. Nd (Fe, b) and SmCo magnets are anisotropic. Magnetic anisotropy refers to the phenomenon that the magnetism of a material changes with direction. The results show that the susceptibility of weak magnets and the magnetization curve of ferromagnets vary with the magnetization direction.

BH max (maximum magnetic energy product) – The point of maximum magnetic energy product of magnetic material with magnetic field strength. The intensity of magnetic field measured by megagaust in fully saturated magnetic materials.

Magnetic induction coercivity( Hcb) – When the permanent magnet is saturated, the B (magnetic induction strength) of the permanent magnet decreases to zero, and the required reverse magnetic field strength is called magnetic induction coercivity. Curie temperature – the temperature at which a material can change between a ferromagnet and a paramagnetic.

Maximum operating temperature Tw ℃  –  One of the magnets loses its magnetism at this temperature.

Demagnetization curve -In the second quadrant of the hysteresis loop, the behavior of the magnetic properties usually described in practical use. Also known as the BH curve. The demagnetization curve square diagram is an important magnetic characteristic index of permanent magnet. When the magnet is in the dynamic working condition, the external reverse magnetic field H or the demagnetizing field HD inside the magnet change periodically. For Nd-Fe-B sintered magnet, B changes periodically demagnetization curve. The closer to the straight line, the better the stability of the magnet under dynamic working conditions.

Size – Magnets include the physical dimensions of any coating or coating.

Dimensional tolerance – Make sure that a product is produced within the allowable size range. The purpose of the tolerance is to specify the tolerance allowed for the manufacture of the magnet.

Gaussian – A unit of magnetic induction. The magnetic performance of NdFeB magnet.

Intrinsic coercivity (Hcj) – The reverse magnetic field strength required to reduce the remanent magnetization MR of the magnet to zero. The unit is OE or a / m. The higher the coercivity, the better the temperature stability.

Isotropic materials – A material that can be magnetized along any axis or direction (nonoriented magnetic material). Opposite to anisotropic magnets.

magnetic field intensity – In history, it was first introduced from the viewpoint of magnetic charge. Similar to the Coulomb law of electric charge, people think that there are two kinds of magnetic charges, positive and negative, and put forward the Coulomb law of magnetic charge. The force exerted by the unit positive magnetic charge in the magnetic field is called the magnetic field strength H.

Magnetic flux density – Another name for magnetic induction intensity, which represents the number of lines of force perpendicular to a unit area. The flux line is usually measured in terms of Gauss (CGS).

Magnetic induction intensity B – The physical quantity describing the strength and direction of magnetic field is a vector. It is usually represented by symbol B. the international unit is Tesla (symbol is t). Magnetic induction is also known as magnetic flux density or flux density. In physics, the strength of magnetic field is expressed by magnetic induction intensity. The greater the magnetic induction intensity is, the stronger the magnetic stress is; and the smaller the magnetic induction, the weaker the magnetic induction.

Material grade – Grade of manufacture of neodymium (neodymium iron boron) magnet. Generally speaking, higher grade materials have stronger magnetic force. In the case of the same type of magnet, the magnetic force of N50 material is much higher than that of N35 material.

Maximum magnetic energy product (BH max) – the point of the maximum magnetic energy product of a magnetic material with magnetic field strength.

Magnetism Melting curve – The hysteresis loop (B / h) curve is the first quadrant part of the magnetic material.

Arctic – The north pole of a magnet is a magnetic north pole that attracts to the earth. It is usually represented by the letter n.

Antarctic – The south pole of a magnet is one that attracts to the earth. It is usually represented by the letter s.

Oester (OE) – magnetization force in CGS units.  

Ferromagnetic materials – Iron, steel, nickel and cobalt are ferromagnetic materials. When they are not affected by external magnetic field, the synthetic magnetic moment produced by molecular current is equal to zero in macroscopic view, so it does not show magnetism.

Direction – Used to describe the direction of magnetization of a material. Orientation direction the direction in which an anisotropic magnet should be magnetized to achieve the best magnetic properties.

Permanent magnet – A magnet, removed from the magnetic field, retains its magnetism. Permanent magnets are “always magnetic”. NdFeB magnets are permanent magnets.

Magnetic pole – The characteristic of a permanent magnet at a particular location. Distinguish North (n) and south pole (s).

Paramagnetic materials – Materials that are not attracted to magnetic fields (wood, plastic, aluminum, etc.). Materials with air permeability slightly greater than 1.

Plating / coating – Most NdFeB magnets are plated or coated to protect the magnet material from corrosion. Neodymium magnet is mainly composed of neodymium, iron and boron. If there is no coating, the iron in the magnet will rust. Most magnets are triple plated nickel – copper – nickel, but some are gold, silver, or black nickel, while others have neodymium magnets coated with epoxy, plastic or rubber.

Tesla – The international unit of magnetic flux density. One Tesla is 10000 Gauss.

Weight – The weight of a single magnet.

Relative permeability – The ratio of medium permeability to vacuum permeability, i.e. μ r = μ g μ o. In CGS system, μ o = 1. In addition, the relative permeability of air is often taken as 1 in practical use, and the relative permeability of copper, aluminum and stainless steel is also approximately 1.

Magnetic conductivity – The ratio of magnetic flux Φ to magnetomotive force F is similar to the conductance in a circuit. It is a physical quantity reflecting the magnetic conductivity of materials.

Magnetic conductivity Pc  – On the demagnetization curve, the ratio of magnetic induction intensity BD to magnetic field intensity HD, namely PC = BD / HD, can be used to estimate the magnetic flux under various conditions. For an isolated magnet, PC is only related to the size of the magnet, and the intersection of demagnetization curve and PC line is the working point of the magnet. The larger PC is, the higher the working point of the magnet is, the more difficult it is to be demagnetized. In general, for an isolated magnet, the larger the orientation length, the larger the PC. Therefore, PC is an important physical quantity in the design of permanent magnetic circuit.

Magnetic energy product (BH) – The unit is coke / m3 (J / m3) or goe 1 · mgoe ≈ 7.96k J/m3. Demagnetization curve The product of B and h at any point on is called magnetic energy product, and the maximum value of B × h is called maximum magnetic energy product (BH) max. Magnetic energy product is one of the important parameters of the energy stored in a constant magnet. The larger the BH max, the greater the magnetic energy.

Remanence (BR) – The unit is Tesla (T) and Gauss (GS) 1gs = 0.0001t. When a magnet is magnetized by an external magnetic field in a closed-circuit environment until the technology is saturated, the external magnetic field is removed. At this time, the magnetic induction strength of the magnet is called remanence. It represents the maximum magnetic flux that a magnet can provide. It can be seen from the demagnetization curve that it corresponds to the case when the air gap is zero, so the magnetic induction intensity of the magnet in the actual magnetic circuit is less than the remanence. Neodymium iron boron (NdFeB) is the most practical permanent magnet material with the highest br content.

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