NdFeB magnetic terms

- Nov 04, 2017 -

Permanent magnet material: permanent magnet material is magnetized by the applied magnetic field does not disappear after the magnetic field, can provide a stable magnetic field to the external space. Commonly used neodymium iron boron magnets measure the following four:


Remanence(Br) the units is Tesla (T) and Gaussian (Gs) 1Gs = 0.0001T


Will be a magnet in a closed-circuit environment is magnetizing the external magnetic field saturation technology to withdraw the external magnetic field, the magnet performance of the magnetic induction at this time we call the remanence. It represents the maximum flux that the magnet can provide. It can be seen from the demagnetization curve that it corresponds to the situation when the air gap is zero, so the magnetic induction of the magnets in the actual magnetic circuit is less than the remanence. NdFeB is Br's highest practical permanent magnet material found today.


Magnetic coercivity (Hcb) units are amperes per meter (A / m) and Oe or 1 Oe≈79.6 A / m


The value of the inverse magnetic field strength needed to demagnetize the magnetic induction to zero when magnetically saturated after magnetization is reverse magnetized is called the coercivity (Hcb). However, the magnetization of the magnet is not zero at this time, but the applied reverse magnetic field and the magnetization of the magnet cancel each other out. (External magnetic induction intensity is zero) At this time if the withdrawal of the external magnetic field, the magnet still has some magnetic properties. The coercivity of NdFeB is generally 11000Oe or more.


The intrinsic coercivity (Hcj) units are amperes per meter (A / m) and Oe 1 Oe≈79.6A / m


The reverse magnetic field strength required to reduce the magnetization of the magnet to zero, which we call intrinsic coercivity. Coercivity is a measure of the intrinsic magnetism of anti-demagnetization capacity of a physical quantity, if the applied magnetic field is equal to the intrinsic coercivity of the magnet, the magnetism of the magnet will be basically eliminated. NdFeB Hcj will decrease with increasing temperature, so need to work in high temperature environment should choose high Hcj grades.


Magnetic energy product (BH) in units of coke / m 3 (J / m3) or high • GOe 1 MGOe≈7. 96k J / m3


The product of B and H at any point on the demagnetization curve is called BH as the energy product and the maximum value of B × H is called the maximum energy product (BH) max. Magneto-energy product is one of the important parameters of the energy stored by the constant magnet. The larger the (BH) max, the larger the magnetic energy contained in the magnet. When designing the magnetic circuit, make the working point of the magnet be near the B and H corresponding to the maximum magnetic energy product as much as possible.


Isotropic Magnet: A magnet that has the same magnetic properties in any direction.


Anisotropic magnets: Different magnetic properties in different directions; And there is a direction, the highest magnetic properties in the orientation of the resulting magnet. Sintered NdFeB permanent magnets are anisotropic magnets.

Orientation direction: anisotropic magnet can get the best magnetic properties of the direction known as the magnet orientation. Also called

"Orientation axis", "easy axis".

Magnetic field strength: refers to the size of the magnetic field somewhere in space, denoted by H, and its unit is amperes per meter (A / m).


Magnetization: refers to the magnetic moment vector sum of the unit volume inside the material, expressed by M, in amperes per meter (A / m).


Magnetic induction: The magnetic induction B is defined as: B = μ0 (H + M), where H and M are the magnetization and the magnetic field strength, respectively, and μ0 is the vacuum permeability. Magnetic induction, also known as magnetic flux density, that is, the magnetic flux per unit area. The unit is Tesla (T).


Flux: The total magnetic flux density in a given area. When the magnetic flux density B is uniformly distributed on the surface A of the magnet, the general formula of the magnetic flux Φ is Φ = B × A. The SI unit of flux is Maxwell.


Relative permeability: The ratio of medium permeability to vacuum permeability, μr

= μ / μo. In CGS system, μo = 1. In addition, the relative permeability of air is often taken as 1 in actual use. In addition, the relative permeability of copper, aluminum and stainless steel is also approximately 1.



Flux: The ratio of flux Φ to flux F, similar to the conductance in a circuit. It is a physical quantity that reflects the magnetic permeability of material.


Magnetic permeability coefficient Pc: Also demagnetization coefficient, in the demagnetization curve, magnetic flux density Bd and magnetic field strength Hd ratio, ie Pc = Bd / Hd, permeability can be used to estimate the flux value under various conditions. For the isolated magnet Pc only with the size of the magnet, demagnetization curve and the intersection of the Pc line is the working point of the magnet, Pc is larger the higher the working point of the magnet, the less susceptible to demagnetization. In general, the larger the orientation length Pc, the larger the orientation length for an isolated magnet. So Pc is an important physical quantity in the design of permanent magnetic circuit.


Article from NdFeB Industry Network

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