Neodymium Iron Boron Magnet Materials

Sintered neodymium-iron-boron (Nd-Fe-B) magnets are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 52 MGOe. Nd-Fe-B is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity, and comes with a wide range of grades, sizes and shapes. With its excellent magnetic characteristics, abundant raw material and relatively low prices, Nd-Fe-B offers more flexibility in designing of new or replace the traditional magnet materials such as ceramic, Alnico and Sm-Co to achieve high efficiency, low cost and more compact devices.

A powder metallurgy process is used in producing sintered Nd-Fe-B magnets. Although sintered Nd-Fe-B is mechanically stronger than Sm-Co magnets and less brittle than other magnets, it should not be used as structural component. Selection of Nd-Fe-B is limited by temperature due to its irreversible loss and moderately high reversible temperature coefficient of Br and Hci. The maximum application temperature is 200 °C for high coercivity grades. Nd-Fe-B magnets are more prone to oxidation than any other magnet alloys. If Nd-Fe-B magnet is to be exposed to humidity, chemically aggressive media such as acids, alkaline solutions salts and harmful gases, coating is recommended. It is not recommended in a hydrogen atmosphere.

Typical Physical Properties
Curie Temperature320 - 380 °C
Coefficient Of Thermal Expansion - Perpendicular1.0 - -3.0 x 10-6 °C-1
Coefficient Of Thermal Expansion - Parallel+5.0 - +8.0 x 10-6 °C-1
Electrical Resistivity120 - 160 Ocm
Density7.4 - 7.8 gcm-3
Vicker's Hardness550 - 650 Hv
Young's Modulus150 - 170 kNmm-2
Bending Strength0.18 - 0.29 kNmm-2
Compressive Strength0.8 - 1.0 kNmm-2