Neodymium magnets - Nd₂Fe₁₄B: specification and technology

Technical knowledge base of sintered neodymium magnets

Sintered neodymium magnet production is an advanced powder metallurgy process in which an alloy of neodymium, iron and boron is formed in a strong magnetic field.

Strip casting. The process begins by melting the charge in an induction furnace under a protective argon atmosphere. The molten metal is poured onto a rotating, water-cooled copper roller and solidifies into thin flakes (SC alloy).
Hydrogen decrepitation and jet milling. The material undergoes the HD (Hydrogen Decrepitation) process — hydrogen penetrates the structure and breaks the ingots into fine particles. Jet mills operating in a nitrogen atmosphere then reduce the powder to a grain diameter of about 3 µm.
Pressing and sintering. The powder is pressed in a strong magnetic field, which aligns the domains and gives the material anisotropy — a preferred direction of magnetisation. The “green” compacts go into vacuum furnaces at about 1050°C. Sintering is followed by two-stage annealing at 900°C and 600°C, which relieves internal stress and dissolves unstable phases.
Machining and magnetisation. The sinters are cut to size with precision wire saws, which limits kerf losses of the costly material. After the protective coating is applied, the magnets are activated in pulse magnetisers with a field of around 5 T.

Neodymium magnet production technology is the manufacture of the strongest permanent magnets available, from an alloy of neodymium, iron and boron. The sintered route covers strip casting, hydrogen decrepitation, jet milling and vacuum sintering with two-stage annealing. The direction of magnetisation is set during pressing in a magnetic field. Thanks to their high coercivity and remanence, NdFeB magnets underpin the miniaturisation of electric motors, electronics and low-emission technologies.

Safety and operation principles

Critical conditions excluding the use of standard NdFeB magnets without specialized shielding:

In acidic, alkaline, organic or dissolving environments (unless you hermetically isolate the magnet from the environment), or radioactive rays
In water or oil (unless you isolate the magnet from the environment or are prepared for the magnet to lose its magnetic properties in a short time)
In an electrically conductive fluid - electrolyte containing water
In an atmosphere containing hydrogen

Material specification

Neodymium magnet (NdFeB) is a sintered rare-earth metal, currently the strongest permanent magnet available. It is characterized by an anisotropic tetragonal crystal structure of Nd2Fe14B. Compared to ferrites, it offers approx. 10 times higher energy density (BH)max, allowing for significant device miniaturization.

Due to the high iron content (approx. 64-68%) and neodymium, the neodymium-rich phase at the grain boundaries is highly reactive. This requires the use of barrier coatings (Ni-Cu-Ni, Epoxy, Parylene). An unprotected magnet oxidizes, forming hydroxides, leading to structural disintegration.

The material is brittle (ceramic-like). Machining is only possible with diamond tools before magnetization. Mechanical shocks should be avoided, as they can lead to micro-cracks (chipping).

Neodymium (Nd, atomic number 60) is a key component of the alloy. It is estimated that approx. 20-30% of neodymium in magnets is actually Praseodymium (Pr). Due to chemical similarity, a Pr-Nd alloy is used, which does not negatively affect the magnet's properties. In high-temperature magnets (UH, EH), part of the neodymium is replaced by Dysprosium (Dy) or Terbium (Tb).

patent discovery year: 1984 (Sagawa / Croat)
Nd atomic number: 60
atomic mass: 144.24 u
electronegativity (Pauling): 1.14
valence: +3
phase melting temp.: 1024°C
boiling point: 3074°C
stable isotopes: 5 (142, 143, 145, 146, 148)
configuration: [Xe] 4f⁴ 6s²

Permanent magnet definition

A permanent magnet is a material with a wide magnetic hysteresis loop, capable of maintaining magnetization after the external magnetizing field is removed. A key parameter is high coercivity (Hcj), preventing spontaneous demagnetization.

Demagnetization and Curie point

Loss of magnetic properties occurs under the influence of temperature (thermal agitation of domains) or an opposing magnetic field. The Curie point (Tc) is the temperature at which the material loses ferromagnetic properties and becomes paramagnetic (for NdFeB approx. 310-350°C).

Nature of magnetism

A physical phenomenon resulting from the angular momentum (spin) of electrons and their orbital motion. In NdFeB magnets, the exchange coupling between iron atoms and rare earths plays a key role.

Evaluation methodology (BH curve)

Professional magnet evaluation is performed using a hysteresigraph (BH analyzer). It determines four key points in the 2nd quadrant of the coordinate system: Br (remanence), HcB (induction coercivity), HcJ (polarization coercivity), and (BH)max.

Flux density (B)

Magnetic induction measured on the magnet surface (surface gauss). This value depends not only on the magnet grade (Br) but also on its geometry (permeance coefficient - Pc).

Coercivity (Hcb / Hcj)

Resistance to demagnetization. Hcb (normal coercivity) defines the point of zero induction, Hcj (intrinsic coercivity) defines the point of zero polarization - this is a key parameter for temperature resistance.

Maximum energy product (BH)max

The maximum amount of magnetic energy stored per unit volume of material. This value (in MGOe) roughly corresponds to the magnet grade number (e.g., N52 has approx. 52 MGOe).

Pull force (attraction)

The perpendicular force required to detach a magnet from a low-carbon ferromagnet, with zero air gap. Laboratory values may differ from real ones due to surface roughness, steel composition, or force application angle.

Shear force (sliding load)

Force acting parallel to the contact surface. It depends directly on the friction coefficient (µ) between the magnet coating and the substrate. For Ni-Cu-Ni coating, it is usually 15-20% of the vertical pull force. Using rubber increases this coefficient.

Measurement procedures

Measurement standards in the DHIT laboratory:

Pull-force test (perpendicular)

Perpendicular detachment at a speed of 10mm/min from a steel plate (St37) with a thickness of min. 10mm, ground.
Shear-force test (sliding)

Parallel sliding. The result is strongly dependent on the coating. For Ni, it is approx. 0.15-0.20 of the vertical force.

Measurement boundary conditions

Variables affecting the measurement result:

Plate thickness: steel that is too thin becomes magnetically saturated, lowering the result.
Positioning: central application of force.
Working area: no plate edges in the immediate vicinity.
Steel grade: preferred pure armco iron or low-carbon steel.
Surface roughness (Ra).
Air gap: even 0.1mm drastically reduces the force.

Anisotropy and magnetization directions

NdFeB sinters are anisotropic materials – the direction of easy magnetization is established during powder pressing in a magnetic field.

Axial

Magnetization vector parallel to the axis of symmetry (height). Most common configuration for cylinders and rings.

Diametrical

Magnetization vector perpendicular to the axis of symmetry (through the diameter).

Radial (multipole)

Specialized orientation (requires a separate mold for pressing). Poles distributed on the circumference.

Magnetic poles are always located on surfaces perpendicular to the orientation direction (easy axis).

Cylindrical magnets

axial: poles on flat bases.
diametrical: poles on the cylinder curves.
radial: multipole on the circumference (for rotors).

Plate magnets (blocks)

through thickness (H): standard.
through width (W).
through length (L).

Ring magnets

axial: standard.
diametrical: 2 poles on the circumference.
radial: special execution.

Alternative production methods (special technologies)

In addition to classic sintering, advanced methods are used to obtain specific properties:

1. Hydrogen method HDDR

The process (Hydrogenation, Disproportionation, Desorption, Recombination) takes place at 750-900°C. It allows obtaining powder with a very fine-grained structure and high coercivity. This material is often used for the production of bonded magnets.

2. Bonded Magnets

A mixture of magnetic powder (NdFeB) with a polymer binder (resin, plastic). Produced by injection molding or compression molding. Although they have weaker magnetic parameters than sintered ones, they are characterized by high shape precision without the need for machining, greater corrosion resistance, and flexibility.

3. Mechanical alloying

Milling powder in ball mills, leading to a nanocrystalline structure. After short annealing (approx. 700°C), a material with very high coercivity is obtained.

Surface engineering (coatings)

Due to the low corrosion resistance of the Nd-rich phase, coatings are mandatory. The thickness and type of coating affect dimensional tolerances and environmental resistance.

Ni-Cu-Ni (standard)

Features: structure: nickel (base) + copper (elasticity/tightness) + nickel (finish).
Color: appearance: silvery gloss.
Price: advantages: best price-to-protection ratio.
Thickness: thickness: 10-20 µm.

Ni-Cu-Ni-Au (gold)

Decorative and functional coating (conductivity).

Layer: top layer: 24k industrial gold (thin layer).
Color: application: medical (biocompatibility), electrical contacts.
Au Thickness: Au thickness: ~0.05-0.1 µm.
Total Thickness: base: requires full Ni-Cu-Ni undercoat.

Ni-Cu-Ni-Cr (chrome)

Resistance: advantages: high resistance to abrasion (friction).
Color: appearance: cold, bluish gloss.
Thickness: thickness: ~15 µm.

Ni-Cu (copper)

Used less frequently as a final layer.

Color: application: lower resistance, mainly aesthetic or as a base.
Abrasion: disadvantage: copper quickly passivates (darkens).
Corrosion: costs: lower than triple layer.
Thickness: thickness: ~10 µm.

Epoxy (resin)

Black electrophoretic or spray coating

Ideal for marine and outdoor applications, as long as it is not exposed to impact.

Color: resistance: excellent against moisture and salt spray.
Corrosion: disadvantage: brittle, prone to mechanical scratches.
Resistance: insulation: electrical.
Thickness: thickness: 15-30 µm.

Rubber coated

Dedicated to automotive and mounting holders.

Color: material: santoprene or synthetic rubber.
Impact: function: increases friction (shear force), protects substrate paint.
Friction: disadvantage: air gap (rubber thickness 0.5mm) significantly reduces perpendicular force.
Thickness: thickness: 0.5 - 1.0 mm.
Chemicals: water resistance: very high.
Force: impact resistance: absorbs shocks.

Plastic overmolding

Full environmental protection.

Color: material: ABS, PP, Nylon.
Impact: tightness: complete (hermetic).
Friction: durability: very high.
Thickness: wall thickness: 1-2 mm.
Chemicals: application: clothing industry, toys.
Force: force reduction: significant (large gap).

Technical parameters of coatings

Detailed comparative data on corrosion resistance (SST and PCT tests):

material	symbol	coating thickness (μm)	corrosion resistance (salt spray) (Hr)	porosity	demagnetization rate	color	PCT (Hr)
Zinc	Zn	10-15	>24	<0.1	<0.2%	White	>16
Colorful zinc	Colorful-Zn	10-15	72	<0.1	<0.1%	Multicolor	>24
Nickel	Ni	10-20	4	<0.5	<0.3%	Silver	>16
Double nickel	Divalent-Ni	15-20	24	<0.2	<0.3%	Silver	>16
Nickel-copper-nickel	Ni-Cu-Ni	15-30	>48	<0.1	<0.1%	Silver	>42
Zinc-nickel alloy	Zn-Ni alloy	10-20	>720	<0.1	<0.1%	Various colors	>72
Third-party epoxy	Epoxy	10-50	>300	-	-	Black	>24
Electroless nickel	electroless Ni	<1	>72	-	-	Silver	>24

Salt chamber test: 37-39°C 5% NaCl PH 6.5-7.0 1.5 ml/Hr
PCT: 120°C, 2atm, 100% RH, 12Hr.

Appearance and characteristics

φ10mm×10mm	Element symbol	Element name	Properties	Usage
	3CrZn	Trivalent chromium zinc	Recently hexavalent chromium has been recognized as an environmentally damaging substance and replaced by trivalent chromium	Electronic parts, industrial tool parts
	Ag	Silver	Silver has the best electrical conductivity of all metals, low contact resistance, and good solderability, but is easy to discolor.	Electronic parts, Connectors, Dishes, Accessories
	Au	Gold	Gold has good corrosion and oxidation resistance and low electrical resistance.	Electronic parts, Electrical parts, Decorations, Accessories
	Cr	Chrome	Chrome has good abrasion and oxidation resistance and does not lose its shine in the atmosphere.	Exterior parts, Medical supplies, Audiovisual equipment, Accessories
	Cu	Copper	Copper discolors easily, so it is used as a base. Used to fill dents and add shine.	Cast products, ABS resin base
	CuZn	Bronze	Brass materials change color easily and are usually used as an undercoat. Brass materials are often used in ancient ornaments.	Ancient colorful ornaments
	Ni	Nickel	Nickel is chemically stable and has good anti-corrosion properties. It can be used for many different purposes and is used as a base for gold plating, chrome plating, etc. May cause skin irritation.	Electronic parts, Connectors, Base plating, Accessories
	NiBlack	Black nickel	Black nickel is an alloy coating made of nickel, zinc, and sulfur. The color may vary depending on the type of plating used as an undercoat.	Decorations, Accessories
	Sn	Tin	Tin has excellent anti-corrosion properties and does not oxidize easily. It does not lose its shine easily and can be safely used in food products.	Food dishes, Cans, Tin items, Decorations, Accessories
	Rh	Rhodium	Rhodium has excellent anti-corrosion properties and does not oxidize easily. It does not lose its shine easily and can be safely used in food products.	Electronic parts, Electrical parts, Audio parts, Decorations, Accessories
	-	Untreated	No surface treatment coating. Rust will easily develop on neodymium magnets.
	-	Nylon	Made without organic solvents and used in food processors and medical devices. Passed the food hygiene act.	Toys, Small items
	-	Polyamide MF305	High impact strength, bending resistance, and possibility of use at high temperature.	Electronic parts, Small items, For bending after painting
-	-	Epoxy MF304	High resin hardness / Flame retardancy adjustment: UL94 / V-0 Certified
-	-	Epoxy MF303	High resin hardness / Easy to polish

Rust resistance test Ni / Zu / Epoxy resin

	Dhit	Company [S]	Other companies	Dhit	Company [T]	Dhit
Duration	HDC coating, Epoxy resin, MF304	Normal epoxy resin	Anti-corrosion Zn primer for Zn car	HDC, Epoxy resin coating, MF305	epoxy resin	NiCuNi, 3 layers, nickel
Before starting test
After 72 hrs
After 312 hrs
After 504 hrs

Salt chamber test: 37-39 °C 5% NaCl PH 6.5-7.0 1.5 ml/Hr
PCT: 120°C, 2atm, 100% RH, 12Hr.

Thermal stability and magnetic losses

Depending on temperature, we distinguish three different types of losses:

reversible (can be undone)
irreversible (cannot be undone)
constant

Reversible temperature loss

temperature area: slightly above maximum operating temperature,
temperature area: slightly above maximum operating temperature
magnet is less magnetic if it is hot
it does not matter how often the magnet is heated and cooled

Irreversible loss

temperature area: significantly above maximum operating temperature
magnet is permanently weakened, even after cooling
repeated heating at the same temperature does not strengthen irreversible losses
magnetization of an irreversibly weakened magnet by a sufficiently strong external magnetic field can restore its original strength

Constant loss of magnetic properties

due to high temperature, the structure of neodymium magnets changes - magnetization is no longer possible

Engineering tables (advanced data)

Mechanical properties
Young's Modulus (E)	160	GPa
Poisson's Ratio (ν)	0.24	-
Compressive strength	1000 - 1100	MPa
Tensile strength	80	MPa
Vickers Hardness (Hv)	560 - 600	Hv
Density	7.4 - 7.6	g/cm³

Thermal properties
Specific heat	460	J/(kg·K)
Thermal conductivity	6 - 9	W/(m·K)
Expansion coefficient (parallel)	5.2 x 10⁻⁶	/°C
Expansion coefficient (perpendicular)	-0.8 x 10⁻⁶	/°C

Standard geometric tolerances (ISO)
Dimension (L, W, H)	±0.05 mm (standard) / ±0.02 mm (precision)
Diameter (D)	±0.05 mm
Flatness	< 0.05 mm
Parallelism	< 0.05 mm
Perpendicularity	< 1°

Magnetic unit converter
1 Tesla (T)		10,000 Gauss (G)
1 kA/m		12.57 Oersted (Oe)
1 MGOe		7.96 kJ/m³

Maximum production dimensions for NdFeB magnets

shape	parameters
cylindrical magnet		dimension
		D(mm)	L(mm)	magnetization direction
	all grades	1.0 ~ 250 mm	≤ 80 mm	axial or radial
ring magnet		dimension
		D(mm)	P(mm)	L(mm)	magnetization direction
	all grades	2.5 ~ 250 mm	0.8 ~ 230 mm	≤ 80 mm	≤ 80 mm
plate magnet		dimension
		L(mm)	W(mm)	H(mm)	magnetization direction
	all grades	≤ 200 mm	≤ 100 mm	≤ 80 mm	≤ 80 mm
segment		dimension
		H(mm)	W(mm)	L(mm)	magnetization direction
	all grades	≤ 70 mm	≤ 100 mm	≤ 200 mm	≤ 80 mm

Magnetic properties of sintered neodymium magnets NdFeB

material type	remanence		coercivity		actual intrinsic force		energy density		operating temperature
	Br(kGs)	Br(T)	coercivity		actual intrinsic force		(BH)max(MGOe)	(BH)max(KJ/m)
	Min. - Max.	Min. - Max.	bHc(kOe)	bHc(kA/m)	iHc(kOe)	iHc(kA/m)	Min. - Max.	Min. - Max.
N30	10.8-11.2	1080-1120	9.8-10.5	780-836	≥12	≥955	28-30	223-239	≤ 80°C
N33	11.4-11.7	1140-1170	10.3-11	820-876	≥12	≥955	31-33	247-263	≤ 80°C
N35	11.7-12.1	1170-1210	10.8-11.5	860-915	≥12	≥955	33-35	263-279	≤ 80°C
N38	12.2-12.6	1220-1260	10.8-11.5	860-915	≥12	≥955	36-38	287-303	≤ 80°C
N40	12.6-12.9	1260-1290	10.5-12.0	860-955	≥12	≥955	38-40	303-318	≤ 80°C
N42	12.9-13.2	1290-1320	10.8-12.0	860-955	≥12	≥955	40-42	318-334	≤ 80°C
N45	13.2-13.7	1320-1370	10.8-12.5	860-995	≥12	≥955	43-45	342-358	≤ 80°C
N48	13.7-14.2	1370-1420	10.8-12.5	860-995	≥12	≥955	45-48	358-382	≤ 80°C
N50	14-14.6	1400-1460	10.8-12.5	860-995	≥12	≥955	47-51	374-406	≤ 80°C
N52	14.2-14.7	1420-1470	10.8-12.5	860-995	≥12	≥955	48-53	380-422	≤ 65°C
N54	14.5-15.1	1450-1510	10.8-12.5	860-995	≥12	≥876	51-55	406-438	≤ 80°C
N30M	10.8-11.2	1080-1120	9.8-10.5	780-836	≥14	≥1114	28-30	223-239	≤100°C
N33M	11.4-11.7	1140-1170	10.3-11	820-876	≥14	≥1114	31-33	247-263	≤100°C
N35M	11.7-12.1	1170-1210	10.8-11.5	860-915	≥14	≥1114	33-35	263-279	≤100°C
N38M	12.2-12.6	1120-1260	10.8-11.5	860-915	≥14	≥1114	36-38	287-303	≤100°C
N40M	12.6-12.9	1260-1290	10.8-12	860-955	≥14	≥1114	38-40	303-318	≤100°C
N42M	12.9-13.2	1290-1320	10.8-12.5	860-995	≥14	≥1114	40-42	318-334	≤100°C
N45M	13.2-13.7	1320-1370	10.8-13	860-1035	≥14	≥1114	43-45	342-358	≤100°C
N48M	13.7-14.2	1370-1420	10.8-12.5	860-995	≥14	≥1114	45-48	358-382	≤100°C
N50M	14-14.6	1400-1460	10.8-12.5	860-995	≥14	≥1114	47-51	374-406	≤100°C
N27H	10.2-10.6	1020-1060	9.5-10.1	756-804	≥17	≥1353	25-27	199-215	≤120°C
N30H	10.8-11.2	1080-1120	10.1-10.6	804-844	≥17	≥1353	28-30	223-239	≤120°C
N33H	11.4-11.7	1140-1170	10.3-11	820-876	≥17	≥1353	31-33	247-263	≤120°C
N35H	11.7-12.1	1170-1210	10.8-11.5	860-915	≥17	≥1353	33-35	263-279	≤120°C
N38H	12.2-12.6	1120-1260	10.8-11.5	860-915	≥17	≥1353	36-38	287-303	≤120°C
N40H	12.6-12.9	1260-1290	10.8-12	860-955	≥17	≥1353	38-40	303-318	≤120°C
N42H	12.9-13.2	1290-1320	10.8-12	860-955	≥17	≥1353	40-42	318-334	≤120°C
N44H	13.2-13.6	1320-1360	10.8-13	860-1035	≥17	≥1353	42-44	334-350	≤120°C
N48H	13.7-14.2	1370-1420	10.8-12.5	860-995	≥17	≥1353	45-48	358-382	≤120°C
N27SH	10.2-10.6	1020-1060	9.5-10.1	756-804	≥20	≥1592	25-27	199-215	≤150°C
N30SH	10.8-11.2	1080-1120	10.1-10.6	804-844	≥20	≥1592	28-30	223-239	≤150°C
N33SH	11.4-11.7	1140-1170	10.3-11	820-876	≥20	≥1592	31-33	247-263	≤150°C
N35SH	11.7-12.1	1170-1210	10.8-11.5	860-915	≥20	≥1592	33-35	263-279	≤150°C
N38SH	12.2-12.6	1120-1260	10.8-11.5	860-915	≥20	≥1592	36-38	287-303	≤150°C
N40SH	12.6-12.9	1260-1290	10.8-12.0	860-955	≥20	≥1592	38-40	303-318	≤150°C
N42SH	12.9-13.2	1290-1320	10.8-12	860-955	≥20	≥1592	40-42	318-334	≤150°C
N45SH	13.2-13.7	1320-1370	10.8-12.5	860-955	≥20	≥1592	43-45	342-358	≤150°C
N25UH	9.8-10.2	980-1020	9.2-9.6	732-764	≥25	≥1990	23-25	183-199	≤180°C
N28UH	10.4-10.8	1040-1080	9.8-10.2	780-812	≥25	≥1990	26-28	207-233	≤180°C
N30UH	10.8-11.2	1080-1120	10.1-10.6	804-844	≥25	≥1990	28-30	223-239	≤180°C
N33UH	11.4-11.7	1140-1170	10.3-11	820-876	≥25	≥1990	31-33	247-263	≤180°C
N35UH	11.7-12.1	1170-1210	10.8-11.5	860-915	≥25	≥1990	33-35	263-279	≤180°C
N38UH	12.2-12.6	1120-1260	10.8-11.5	860-915	≥25	≥1990	36-38	287-303	≤180°C
N40UH	12.6-12.9	1260-1290	10.5-12.0	860-955	≥25	≥1990	38-40	303-318	≤180°C
N25EH	9.8-10.2	980-1020	9.2-9.6	732-764	≥30	≥2388	23-25	183-199	≤200°C
N28EH	10.4-10.8	1040-1080	9.8-10.2	780-812	≥30	≥2388	26-28	207-223	≤200°C
N30EH	10.8-11.2	1080-1120	10.1-10.6	804-844	≥30	≥2388	28-30	223-239	≤200°C
N33EH	11.4-11.7	1140-1170	10.3-11	820-876	≥30	≥2388	31-33	247-263	≤200°C
N35EH	11.7-12.1	1170-1210	10.8-11.5	860-915	≥30	≥2388	33-35	263-279	≤200°C
N38EH	12.2-12.5	1120-1250	≥11.3	≥899	≥30	≥2388	36-39	287-310	≤200°C
N40EH	12.5-12.8	1250-1280	≥11.6	≥923	≥30	≥2388	38-41	302-326	≤200°C
N42EH	12.8-13.2	1280-1320	≥11.7	≥931	≥30	≥2388	40-43	318-342	≤200°C
N28AH	10.4-10.8	1040-1080	≥9.9	≥787	≥33	≥2624	26-29	207-231	≤230°C
N30AH	10.8-11.3	1080-1130	≥10.3	≥819	≥33	≥2624	28-31	223-247	≤230°C
N33AH	11.3-11.7	1130-1170	≥10.6	≥843	≥33	≥2624	31-34	247-271	≤230°C
N35AH	11.7-12.2	1170-1120	≥11.0	≥876	≥33	≥2624	33-36	263-287	≤230°C
N38AH	12.2-12.5	1120-1250	≥11.3	≥899	≥33	≥2624	36-39	287-310	≤230°C
N40AH	12.5-12.8	1250-1280	≥11.6	≥923	≥33	≥2624	38-41	302-326	≤230°C

* The above-mentioned data regarding magnetic and physical properties are given at room temperature (20°C). The maximum operating temperature of the magnet may change due to the length-to-diameter ratio, coating thickness, and other environmental factors. Additional grades are available. Please contact us for information.

Temperature properties of neodymium magnets

The table below contains information about the maximum operating temperature (Maximum Operating Temperature) and Curie temperature (Curie Temperature) for individual grades ("N Grade"). Knowledge of these parameters is particularly important when selecting a magnet for applications in elevated temperature conditions.

magnet type/grade	maximum operating temperature	Curie temperature
N	80°C / 176°F	310°C / 590°F
NM	100°C / 212°F	340°C / 644°F
NH	120°C / 248°F	340°C / 644°F
NSH	150°C / 302°F	340°C / 644°F
NUH	180°C / 356°F	350°C / 662°F
NEH	200°C / 392°F	350°C / 662°F
NAH	230°C / 446°F	350°C / 662°F

Influence of Heavy Rare Earth Elements (Dy/Tb/Ho)

The table below illustrates the classification of sintered materials based on production technology. The blue area (HREE FREE) indicates magnets produced without the use of heavy rare earth elements. The yellow area requires doping with Dysprosium (Dy) or Terbium (Tb) to obtain high coercivity.

HREE FREE (Without heavy elements)

With heavy elements (Dy/Tb/Ho)

Br (kGs)	Max Temp
Br (kGs)	80°C (N)	100°C (M)	120°C (H)	150°C (SH)	180°C (UH)	200°C (EH)	220°C (AH)	250°C (TH)
14.8 - 15.2	60N	60M	60H	60SH	-	-	-	-
14.6 - 14.9	58N	58M	58H	58SH	-	-	-	-
14.3 - 14.6	55N	55M	55H	55SH	54UH	-	-	-
14.0 - 14.3	52N	52M	52H	52SH	52UH	52EH	-	-
13.7 - 14.0	50N	50M	50H	50SH	50UH	50EH	-	-
13.2 - 13.6	48N	48M	48H	48SH	48UH	48EH	-	-
12.8 - 13.2	45N	45M	45H	45SH	45UH	45EH	45AH	-
12.5 - 12.8	42N	42M	42H	42SH	42UH	42EH	42AH	-
12.2 - 12.5	40N	40M	40H	40SH	40UH	40EH	40AH	40TH
11.8 - 12.2	38N	38M	38H	38SH	38UH	38EH	38AH	38TH
11.3 - 11.7	35N	35M	35H	35SH	35UH	35EH	35AH	35TH
Hcj (kOe) →	12	14	17	20	25	30	35	40