A brief introduction to NdFeB (neodymium) magnet, “the magnet king”

A brief introduction to NdFeB (neodymium) magnet, “the magnet king”

 

NdFeB (neodymium magnet), simply speaking, is a kind of magnet, but unlike most of the magnets we see, it’s called “the magnet king” because of its excellent magnetic properties. NdFeB are praseodymium metal, boron iron and other alloys, it is also called magnetic steel. NdFeB contains a large amount of rare earth element neodymium, iron and boron to form the Nd2Fe14B tetragonal crystalline structure. so it is hard and brittle in character.

 

Molecular structure

Characteristics

Because the surface is easy to be oxidized corrosion, NdFe must be coated on the surface. Surface chemical passivation is one of the best solutions. As a kind of rare earth permanent magnet, NdFeB has the advantages of extremely high magnetic energy product, high coercive force, and high energy density at the same time, which is widely used in modern industry and electronic technology. So NdFeB makes it possible for the instruments and meters, electronic motor, magnetization of the magnetic separation equipment to be minimized, lightweighted, thinned.

 

Applications

Neodymium magnets have replaced alnico and ferrite magnets in many of the myriad applications in modern technology where strong permanent magnets are required, because their greater strength allows the use of smaller, lighter magnets for a given application. Some examples are:

• Head actuators for computer hard disks
• Mechanical e-cigarette firing switches
• Locks for doors
• Loudspeakers and headphones
• Mobile phone speakers, taptic feedback and auto focus actuators
• Magnetic bearings and couplings
• Benchtop NMR spectrometers
  • Electric motors: (Using neodymium magnets in electric motors can reduce their power consumption by half.)
  • Cordless tools
  • Servomotors
  • Lifting and compressor motors
  • Synchronous motors
  • Spindle and stepper motors
  • Electrical power steering
  • Drive motors for hybrid and electric vehicles. The electric motors of each Toyota Prius require one kilogram (2.2 lb) of neodymium.
• Actuators
• Electric generators for wind turbines (only those with permanent magnet excitation)
• Alignment of nanocellulose chiral nematic suspensions to fabricate cellulose nanocrystals films with tuneable specular and off-specular optical response
• Voice coil
• Retail media case decouplers[clarification needed]
• In process industries, powerful neodymium magnets are used to catch foreign bodies and protect product and processes

 

Grades

Neodymium magnets are graded according to their maximum energy product, which relates to the magnetic flux output per unit volume. Higher values indicate stronger magnets. For sintered NdFeB magnets, there is a widely recognized international classification. Their values range from 28 up to 52. The first letter N before the values is short for neodymium, meaning sintered NdFeB magnets. Letters following the values indicate intrinsic coercivity and maximum operating temperatures (positively correlated with the Curie temperature), which range from default (up to 80 ℃ or 176 ℉) to AH (230℃ or 446 ℉).

Grades of sintered NdFeB magnets:

N30 – N52

N30M – N50M

N30H – N50H

N30SH – N48SH

N30UH – N42UH

N28EH – N40EH

N28AH – N35AH

Magnetic properties of various grades of NdFeB materials

Material	Remanence (minimum)		Coercivity (minimum)		Coercivity (minimum)		Maximum Magnetic Energy Product		Density	Temperature Coefficient		Curie	Maximum Service Temperature	Recoil
												Temperature		Permeability
Grade	Br		Hcj		Hcb		（BH）max		D	αBr	αHcj	Tc	Tw	μrec
	Gs	mT	Oe	KA/m	Oe	KA/m	MGOe	KJ/m3	g/m3	%/ ℃	%/ ℃	℃	℃	—
N42	12800~13300	1280~1330	12000	955	11600	923	40~43	318~342	7.5	-0.12	-0.6	320	80	1.05
N45	13300~13700	1330~1370	12000	955	11000	876	43~46	342~366	7.5	-0.12	-0.6	320	80	1.05
N48	13700~14200	1370~1420	12000	955	11200	892	46~49	366~390	7.5	-0.12	-0.6	320	80	1.05
N50	13900~14400	1390~1440	11000	876.00	10500	836.00	47~51	374~406	7.55	-0.12	-0.6	320	80	1.05
N52	14200~14700	1420~1470	11000	876.00	10500	836.00	49~53	390~422	7.55	-0.12	-0.6	320	80	1.05
N42M	12800~13300	1280~1320	14000	1114.00	12000	955.00	40~43	318~342	7.5	-0.12	-0.6	320	100	1.05
N45M	13300~13700	1330~1370	14000	1114.00	12500	995.00	43~46	342~366	7.5	-0.12	-0.6	320	100	1.05
N48M	13600~14200	1360~1420	14000	1114.00	12800	1019.00	45~49	358~390	7.55	-0.12	-0.6	320	100	1.05
N50M	13900~14400	1390~1440	14000	1114.00	13000	1035.00	47~51	374~406	7.55	-0.12	-0.6	320	100	1.05
N52M	14200~14700	1420~1470	13000	1035.00	12500	995.00	49~53	390~422	7.55	-0.12	-0.6	320	100	1.05
N42H	12800~13300	1280~1330	17000	1353.00	12000	955.00	40~43	318~342	7.55	-0.12	-0.6	320	120	1.05
N45H	13300~13700	1330~1370	17000	1353.00	12100	963.00	43~46	342~366	7.55	-0.12	-0.6	320	120	1.05
N48H	13600~14200	1360~1420	17000	1353.00	12900	1027.00	45~49	358~390	7.6	-0.12	-0.6	320	120	1.05
N50H	13900~14400	1390~1440	16000	1274.00	13000	1035.00	47~51	374~406	7.6	-0.12	-0.6	320	120	1.05
N42SH	12800~13200	1280~1320	20000	1592.00	12200	971.00	40~43	318~342	7.55	-0.11	-0.55	320	150	1.05
N45SH	13200~13700	1320~1370	20000	1592.00	12300	979.00	43~46	342~366	7.6	-0.11	-0.55	320	150	1.05
N48SH	13600~14200	1360~1420	19000	1512.00	12500	995.00	45~49	358~390	7.6	-0.11	-0.55	320	150	1.05
N28UH	10200~10800	1020~1080	25000	1990.00	9600	764.00	26~29	207~231	7.5	-0.1	-0.51	320	180	1.05
N30UH	10800~11300	1080~1130	25000	1990.00	10200	812.00	28~31	223~247	7.5	-0.1	-0.51	320	180	1.05
N33UH	11300~11700	1130~1170	25000	1990.00	10700	852.00	31~34	247~271	7.55	-0.1	-0.51	320	180	1.05
N35UH	11700~12200	1170~1220	25000	1990.00	10800	860.00	33~36	263~287	7.55	-0.1	-0.51	320	180	1.05
N38UH	12200~12500	1220~1250	25000	1990.00	11000	876.00	36~39	287~310	7.6	-0.1	-0.48	320	180	1.05
N40UH	12500~12800	1250~1280	25000	1990.00	11500	915.00	38~41	302~326	7.6	-0.1	-0.48	320	180	1.05
N42UH	12700~13200	1270~1320	24000	1910.00	12200	971.00	39~43	310~342	7.6	-0.1	-0.48	320	180	1.05
N45UH	13200~13700	1320~1370	24000	1910.00	12300	979.00	43~46	342~366	7.6	-0.1	-0.48	320	180	1.05
N28EH	10400~10900	1040~1090	30000	2388.00	9800	780.00	26~29	207~231	7.6	-0.09	-0.48	320	200	1.05
N30EH	10800~11300	1080~1130	30000	2388.00	10200	812.00	28~31	223~247	7.6	-0.09	-0.48	320	200	1.05
N33EH	11300~11700	1130~1170	30000	2388.00	10300	820.00	31~34	247~271	7.6	-0.09	-0.48	320	200	1.05
N35EH	11700~12200	1170~1220	30000	2388.00	10500	836.00	33~36	263~287	7.6	-0.09	-0.48	320	200	1.05
N38EH	12000~12500	1200~1250	30000	2388.00	11500	915.00	35~39	279~310	7.6	-0.09	-0.48	320	200	1.05
N28AH	10200~10900	1020~1090	34000	2706.00	9800	780.00	25~29	199~231	7.6	-0.09	-0.48	320	240	1.05
N30AH	10700~11300	1070~1130	34000	2706.00	10200	812.00	27~31	215~247	7.6	-0.09	-0.48	320	240	1.05
N33AH	11100~11700	1110~1170	34000	2706.00	10300	820.00	30~34	239~271	7.6	-0.09	-0.48	320	240	1.05
N35AH	11700~12200	1170~1220	34000	2706.00	10500	836.00	32~36	255~287	7.6	-0.09	-0.48	320	240	1.05

The largest deposit and reserve of rare earth is in Bayan’obo mine, Inner Mondolia, China.  Baotou bayan’obo mine is the largest rare earth mine in the world.