Neodymium (NdFeB) magnets
Neodymium magnets are the most powerful magnets in present with excellet magnetic properties, like remanence and energy product. Neodymium magnets are rare-earth metal based, main components are iron (Fe), neodymium (Nd) and boron (B). Other elements are mixed into the final alloy, like cobalt (Co), dysprozium (Dy) - these elements are added to improve magnetic parameters (remanence, coercivity) and thermal stability (maximum working temperature).
Neodymium magnets are pressed in magnetic field where magnetic domains are alligned into one direction and finally sintered in special vacuum sintering rooms. The final stage is coating by nickel or zinc to prevent undesired oxidation. This is why neodymium magnets are nice, glossy and smooth-faced. NdFeB magnets can be coated also other ways: gold, chrome, epoxy coating, passivation and the most advanced technology is aluminium and titanium nitride coating.
Neodymium magnets are usually supplied as anisotropic, working temperature is between +80 and +240°C depending on material grade.
Table of magnetic properties of neodymium magnets:
|Coercivity Hc (kA/m)||
Max. energy product
Max. working temp.*
|Normal Hcb||Intrinsic Hci|
|N30||1.08 - 1.13||>= 796||>= 1353||223 - 247||80 - 240|
|N33||1.13 - 1.17||>= 812||>= 1353||247 - 271||80 - 240|
|N35||1.17 - 1.22||>= 868||>= 955||263 - 287||80 - 200|
|N38||1.22 - 1.25||>= 899||>= 955||287 - 310||80 - 180|
|N40||1.25 - 1.28||>= 907||>= 955||302 - 326||80 - 180|
|N42||1.28 - 1.32||>= 915||>= 955||318 - 342||80 - 150|
|N45||1.32 - 1.38||>= 923||>= 955||342 - 366||80 - 150|
|N48||1.38 - 1.42||>= 923||>= 955||366 - 390||80 - 120|
|N50||1.40 - 1.45||>= 796||>= 796||382 - 406||60 - 100|
|N52||1.43 - 1.48||>= 796||>= 876||398 - 422||60|
|N54||1.45 - 1.51||>= 939||>= 875||405 - 437||60|
no code - Tw <=80°C (for N52 and N54 max. 60°C)
M - Tw <=100°C
H - Tw <=120°C
SH - Tw <=150°C
UH - Tw <=180°C
EH - Tw <=200°C
AH - Tw <=240°C
Neodymium magnets are hard, brittle and sensitive to crack, so machining is problematic because the protective coating is corrupted. Machining can be carried out by grinding with diamond tools, but the coating must be repaired.
NdFeB magnets have excellent resistance to external magnetic fields and in normal conditions keep their magnetic properties during long time.
Other magnetic and mechanic parameters of neodymium magnets:
|Temp. coefficient of Br (%/°C)||Temp. coefficient of Hci (%/°C)||Magnetizing field (kA/m)||Curie temp. (°C)||Density (g/cm3)||Hardness (Hv)|
|- 0.12||- 0.6||2400||310 - 340||7.5||570|