China Neodymium And Ferrite Magnets Manufacturer & Supplier 
A 42H grade magnet refers to a neodymium-iron-boron magnet that can operate normally at temperatures below 120°C. In practical applications and testing, some people may wonder why the surface magnetic field of a 42H magnet can still be measured to be above 500mT (5000 Gauss). Isn't it supposed to be around 4200 Gauss at most?
Actually, this phenomenon is not abnormal, but rather caused by insufficient understanding of the relationship between the grade of the magnet and its surface magnetic properties.
Firstly, the "H" in 42H stands for high coercivity, which primarily enhances the anti-demagnetization capability and temperature resistance without significantly reducing the remanence. It is not much different from ordinary N42. Under reasonable structural dimensions, 42H fully possesses the magnetic properties to achieve a surface magnetic field of over 500mT.
42H Hollow Cylindrical Neodymium Magnet
Surface magnetic flux density is not only dependent on the material grade but also influenced by the magnet thickness. Even if it is not the highest grade, as long as the thickness is sufficient, the surface magnetic value can still be very high. For example, an N42 grade Ø15×25mm cylindrical magnet achieves a significant flux concentration effect due to its axial thickness of 25mm, it exhibits significant flux concentration, achieving a measured surface magnetic field of approximately 5450 Gauss (≈545 mT). Similarly, a rectangular block magnet of grade N42M measuring 9×12×12mm, with a thickness of 9mm, can also be measured to have a surface magnetic field of 5010 Gauss (≈501 mT).
Therefore, a surface magnetic field exceeding 500 mT for 42H magnets is a normal phenomenon under specific conditions. Ordinary magnets with thicknesses of 3mm or 5mm generally cannot achieve such high values.
The above explains how 42H magnets can exhibit surface magnetic fields exceeding 500 mT. We hope this information is helpful to you.
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