Permanent Magnet Stability

Permanent Magnet Stability – The ability of a permanent magnet to support an external magnetic field results from small magnetic domains “locked” in position by crystal anisotropy within the magnet material. Once established by initial magnetization, these positions are held until acted upon by forces exceeding those that lock the domains. The energy required to disturb the magnetic field produced by a magnet varies for each type of material. Permanent magnets can be produced with extremely high coercive forces (Hc) that will maintain domain alignment in the presence of high external magnetic fields. Stability can be described as the repeated magnetic performance of a material under specific conditions over the life of the magnet.

Factors affecting magnet stability include time, temperature, reluctance changes, adverse fields, radiation, shock, stress, and vibration.

permanent magnet stability

permanent magnet stability

Time

The effect of time on modern permanent magnets is minimal. Studies have shown that permanent magnets will see changes immediately after magnetization. These changes, known as “magnetic creep”, occur as less stable domains are affected by fluctuations in thermal or magnetic energy, even in a thermally stable environment. This variation is reduced as the number of unstable domains decreases. Rare Earth magnets are not as likely to experience this effect because of their extremely high coercivities. Long-term time versus flux studies have shown that a newly magnetized magnet will lose a minor percent of its flux as a function of age. Over 100,000 hours, these losses are in the range of essentially zero for Samarium Cobalt materials to less than 3% for Alnico 5 materials at low permeance coefficients.

Temperature

Temperature effects fall into three categories:

  • Reversible losses.
  • Irreversible but recoverable losses.
  • Irreversible and unrecoverable losses.

Reversible losses

Permanent Magnet Stability – These are losses that are recovered when the magnet returns to its original temperature. Reversible losses cannot be eliminated by magnet stabilization. Reversible losses are described by the Reversible Temperature Coefficients (Tc), shown in table 5.1. Tc is expressed as % per degree Centigrade. These figures vary for specific grades of each material but are representative of the class of material as a whole. It is because the temperature coefficients of Br and Hc are significantly different that the demagnetization curve develops a “knee” at elevated temperatures.

Surface Protection and Coatings

 

countersunk mounting magnet

Countersunk Mounting Magnet W/2 Countersunk Holes

Countersunk Mounting Magnet W/2 Countersunk Holes, Countersink Neodymium Channel Holding Magnet, NdFeB Channel Mounting Magnet, Magnet in Steel Channel Countersunk Countersunk Mounting Magnet W/2 Countersunk Holes Feature: Part No.: HSNIB-50 Dimensions: L(50mm) * L1(40mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 27 (KG) Shape: Rectangular / Block / Bar Material: Countersunk / Countersink Neodymium Magnets / […]

neodymium magnet channel

Mounting Countersunk Neodymium Magnet Channel

Mounting Countersunk Neodymium Magnet Channel, Countersunk Channel Neodymium Holding Magnet, NdFeB Mounting Magnet Channel, Rectangular Pot Magnet W/2 Countersunk Holes Mounting Countersunk Neodymium Magnet Channel Feature: Part No.: HSNIB-40 Dimensions: L(40mm) * L1(30mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 17 (KG) Shape: Rectangular / Block / Bar Material: Countersunk / Countersink Neodymium Magnets / Steel Shell […]

countersunk rectangle channel magnet

Neodymium Countersunk Rectangle Channel Magnet

Neodymium Countersunk Rectangle Channel Magnet, NdFeB Countersunk Square Magnet in Steel, Countersunk M3 Screw Hole Clamp Neodymium Strong Holding Magnet, Rectangular Channel Mounting Magnet Assembly Neodymium Countersunk Rectangle Channel Magnet Feature: Part No.: HSNIA-30 Dimensions: L(30mm) * L1(15mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 16 (KG) Material: Countersunk / Countersink Neodymium Magnets / Steel Shell […]

channel countersunk magnet

Neo Rectangular Channel Countersunk Magnet

Neo Rectangular Channel Countersunk Magnet, U-Channel Magnet With Countersunk Hole, Licensed NdFeB Square Channel Assemblies, Powerful Neodymium Channel Countersink Magnet Neo Rectangular Channel Countersunk Magnet Feature: Part No.: HSNIA-20 Shape: Square / Rectangular Dimensions: L(20mm) * L1(10mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 8 (KG) Material: Countersunk / Countersink Neodymium Magnets / Steel Shell Pot […]

ndfeb channel magnet with countersunk hole

NdFeB Channel Magnet w/ Countersunk Hole

NdFeB Channel Magnet w/ Countersunk Hole, Square NdFeB Channel Countersunk Mounting Magnets, Neodymium Magnet Plate Catch with Yoke, Rectangular Channel Magnet Assembly, Square Countersink Cup Magnets with screw NdFeB Channel Magnet with Countersunk Feature: Part No.: HSNIA-15 Dimensions: L(15mm) * L1(7.5mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 7 (KG) Material: Countersunk / Countersink Neodymium Magnets / Steel Shell Pot […]

countersunk channel magnet

NdFeB Countersunk Channel Magnet

NdFeB Countersunk Channel Magnet, NdFeB Countersunk Square Magnet in Steel, Channel Magnet w/ Countersunk Hole, Rectangular Cup Magnet w/ Countersunk Hole, Square Type Block Pot Magnets NdFeB Countersunk Channel Magnet Feature: Part No.: HSNIA-10 Dimensions: L(10mm) * L1(5mm) * W(13.5mm) * H(5mm) * D1(3.3mm) * D2(6.5mm) Holding Force: 4 (KG) Material: Countersunk / Countersink Neodymium Magnets / Steel Shell […]