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NdFeB magnets come in different grades, such as N42, N52 or N42SH. What do these numbers mean? What characteristics of magnets are involved in various grades?

In general, higher numbers indicate stronger magnets. N52 is more magnetic than N42. These figures come from the actual material properties, which are expressed as the maximum magnetic energy product of the magnet material. It represents the demagnetization curve of the magnet. If you have two magnets of the same size and different brands, you will find that the magnet of high brand is much stronger.

## How to measure the strength of a magnet?

This requires testing the magnetic field strength of a magnet. Gauss meter is usually used.

Magnets are commonly used in electric motors, generators, refrigerators, credit and debit cards, and in electronic devices such as electric guitar pickups, stereo speakers, and computer hard drives. They can be permanent magnets made of the natural magnetic form of iron or alloy, or they can be electromagnets. When the current passes through the wire coil wound on the iron core, the electromagnetic field will be generated. There are several factors that affect the strength of the magnetic field, and there are many ways to determine the strength of these magnetic fields. Both are described in the following article. Consider the properties of magnets. The magnetic properties are described using the following characteristics: coercivity of the magnetic field, abbreviated as Hc.

The magnetic field intensity is expressed in Gauss, which depends on the size, shape and grade of the product.

### Use the following characteristics to describe the magnetic properties:

• Coercivity of magnetic field, abbreviated as Hc. This represents the point where the magnet can be blocked by another magnetic field. The higher the number, the more difficult it is to stop the magnet.
• The remaining flux density, abbreviated as br. This is the maximum flux that a magnet can produce.
• The general density of energy (Bmax) is related to the density of magnetic flux. The higher the number, the stronger the magnet will be.
• The temperature coefficient of the residual magnetic flux density (abbreviated as tcoef of Br, expressed as a percentage of centigrade) describes how the magnetic flux decreases as the temperature of the magnet increases. The tcoef of Br is 0.1, which means that if the temperature of the magnet increases by 100 ° C (180 ° f), the magnetic flux will decrease by 10%.
• The maximum working temperature (Tmax) is the maximum temperature at which the magnet can work without losing its magnetic field strength. Once the temperature drops below Tmax, the magnet will recover the full strength of its magnetic field. If the magnet is heated above Tmax and cooled to normal working temperature, it will lose some strength of its magnetic field permanently. However, if the magnet is heated to Curie temperature (tcuie for short), it is not recommended.

### Materials for making permanent magnets

Permanent magnets are usually made of one of the following materials:

• Neodymium, iron and boron. This material has the highest level of magnetic flux density (12800 Gauss), coercive force of magnetic field (12300 Oster) and general energy density (40). It has the lowest maximum operating temperature and Curie temperature (150 ° C or 302 ° F and 310 ° C or 590 ° f respectively), and the temperature coefficient is – 0.12.
• The magnetic field coercivity of Mar CO is 9200 OST, but the magnetic flux density is 10500 Gauss and the total energy density is 26. At 300 ° C (572 ° f), its maximum operating temperature is much higher than the Curie temperature of Nd, Fe and B magnets; at 750 ° C (1382 ° f), its maximum operating temperature is also higher. The temperature coefficient is 0.04.
• Alnico is an alloy of aluminum, nickel and cobalt. Its magnetic flux density is close to that of Nd, Fe and B magnets (12500 Gauss), but the coercivity of magnetic field is much lower (640 Oster). Therefore, the general energy density is only 55. At 540 ° C (1004 ° f), its maximum operating temperature is higher than that of SA cobalt. The Curie temperature is higher, 860 ° C (1580 ° f), and the temperature coefficient is 0.02.
• The magnetic flux density and total energy density of ceramic magnet and ferrite magnet are much lower than those of other materials, 3900 Gauss and 3.5 Gauss, respectively. However, its flux density at 3200 osts is much better than that of Al Ni Co alloy. The maximum operating temperature is the same as that of SA cobalt, but the Curie temperature is much lower, which is 460 ° C (860 ° f), and the temperature coefficient is – 0.2. Therefore, the field strength loss of these magnets in heat is faster than that of magnets made of any other material.

### Typical Physical and Chemical Properties of Some Magnetic Materials

Performance Name Unit Sintered NdFeB Bonded NdFeB Sintered Sm2Co17 Sintered SmCo5 Sintered Ferrite Injection Ferrite AlNiCo
Maximum Energy Product ((BH)max) MGOe 28 ~ 52 2 ~ 13 16 ~ 32 14 ~ 24 2 ~ 5 1 ~ 2 1 ~ 13
Intrinsic Coercivity (Hcj) kOe 11 ~ 35 6 ~ 14 8 ~ 35 15 ~ 30 2 ~ 5 2 ~ 4 1 ~ 2
Temperature Coefficient of Br (α) %/°C -0.09 ~ -0.12 -0.10 ~ -0.13 -0.030 ~ -0.045 -0.035 ~ -0.050 -0.2 -0.2 -0.02
Temperature Coefficient of Hcj (β) %/°C -0.40 ~ -0.60 -0.40 ~ -0.60 -0.20 ~ -0.30 -0.20 ~ -0.30 0.3 0.3 0.01 ~ 0.03
Curie Temperature (Tc) °C 310 ~370 300 ~ 350 800 ~ 850 700 ~ 750 450 ~ 480 450 ~ 480 750 ~ 890
Maximum Working Temperature (Tw) °C 230 150 350 250 250 150 500
Recoil Permeability (μrec) 1.05 1.2 1.05 ~ 1.10 1.05 1.05 ~ 1.20 1.05 ~ 1.20 1.70 ~ 4.70
Density (ρ) g/cm3 7.4 ~7.7 4.0 ~ 6.5 8.3 ~ 8.5 8.1 ~ 8.4 4.8 ~ 5.2 3.3 ~ 3.9 6.9 ~ 7.4
Resistivity (ρ) μΩ·m 1.4 ~ 1.6 0.8 ~ 0.9 0.5 ~ 0.6 > 1×108 > 1×108 > 5×103
Thermal Conductivity (λ) W/(m·°C) 8 ~ 10 12 13
Vickers Hardness (Hv) MPa 500 ~ 600 500 ~ 600 400 ~ 500 480 ~ 580 520 ~ 630
Rockwell Hardness (HRB) MPa 35 ~ 45
Compressive Strenght (σbc) MPa 1000 ~ 1100 200 800 1000
Bending Strength (σbb) MPa 200 ~ 400 150 180 300 90 ~ 160
Tensile Strength (σb) MPa 80 ~ 90 58 35 40 < 100 45 ~ 110
Young’s Modulus (E) GPa 150 ~ 200 120 130
Thermal Expansivity (α) 10-6/°C ∥3 ~ 4 1 ~ 2 ∥7 ~ 9 ∥5 ~ 7 7 ~ 15
⊥1 ~ 3 ⊥10 ~ 12 ⊥11 ~ 13
Corrosion resistance ★★☆☆☆ ★★★☆☆ ★★★★☆ ★★★★☆ ★★★★☆ ★★★★☆ ★★★★★

Note:

• The above data are only for reference, specific magnets maybe have different values.

## What kind of magnet should I choose?

This depends on the range of application of the magnet, such as: need to absorb multiple objects, at what temperature of the working environment.
Comparison of NdFeB with other magnets

 Type Maximum magnetic energy product (mega gaussoersted) NdFeB 35-52 Samarium cobalt 26 26 AlNiCo 5.4 Ferrite 3.4 Other 0.6-1.2

NdFeB magnets are the most powerful type of permanent magnets available. The progress of magnets is the history of improving coercivity. Neodymium magnets are all strong and are not easy to demagnetize than other types of magnets.

## Where does the number of N come from?

First, n stands for NdFeB, then the number stands for magnetic energy product, and then the letter stands for coercivity characteristics. For example, N35 without letter stands for the common type of N35, m for medium coercivity, h for high coercivity, etc.

### Verification standard

The grade or brand of a magnet is determined by four physical characteristics: remanence BR, coercivity HCB, intrinsic coercivity Hcj and maximum magnetic energy product (BH) max.

### Give an example

Let’s take the n42h magnet as an example.
N: It stands for NdFeB.
42: represents the maximum magnetic energy product of 42mgoe.
H: It represents high coercivity
The figure below is the international standard for physical parameters and properties of sintered NdFeB (small part).

### The digital meaning of 42

We can see that the remanence data and maximum energy product data of N42 / N42M / N42H are the same,
The remanence and maximum energy product of N42 is higher than that of N35, which indicates that its magnetism is stronger than that of N35 and lower than that of N52, which indicates that its magnetism is lower than that of N52.
From this we can get a result: remanence determines the maximum magnetic energy product, the higher the brand number, the stronger the magnetic.

### The meaning of H

From the figure above, we can see that the coercivity and intrinsic coercivity of N42H are higher than those of N42 and N42M, so their working temperature is different. N42 can only work below 80 ℃, N42M can work at 100 ℃ without demagnetization, and N42H can work at 120 ℃.
From this we can get a result: the highest working temperature is determined by the coercivity and intrinsic coercivity. The higher the coercivity is, the higher the working temperature is.
From the above, we know that remanence, coercivity, intrinsic coercivity and magnetic energy product determine the grade / grade of magnet.

### The origin of data

After the material is sintered into blank, a drawing will be obtained by demagnetization curve instrument, which is BH demagnetization curve. These physical parameters are obtained by BH demagnetization curve.

#### Diagram of BH demagnetization curve

BH demagnetization curve is the most important index to judge the grade of magnet.
It is a drawing printed out by demagnetization curve tester of magnet material. From BH demagnetization curve, we can see four physical parameters of approved magnet grade / Brand: remanence, coercivity, intrinsic coercivity and maximum magnetic energy product.
Let’s take a look at N42H, the physical parameter standard of magnet grade.

#### Physical parameter standard

Figure 1

The figure above is the physical parameter standard of N42H, so let’s see whether the BH demagnetization curve figure (2) below is up to the standard according to the N42H brand material test.

Figure 2

#### Look at the picture

The maximum value of remanence BH: B line is 13.17kgs, which meets the standard
Coercivity HCB: the value of H-line diagonal point is 12.58koe, which meets the standard
Intrinsic coercivity Hcj: H 85koe, which is in line with the standard
Maximum magnetic energy product (BH) max: the tangent point with B ~ H curve is the maximum magnetic energy product point of this B ~ H curve, and its value is the maximum magnetic energy product. This value is 41.52mgoe, which meets the standard.

#### Verification results

The final verification result: the data obtained from Figure 2 (BH demagnetization curve) meets the physical parameter standard of N42H in Figure 1. According to this, the N42H magnet grade material tested is qualified.

TOPS or Regular Magnets

Remanence
Br
Coercivity
HcJ
Coercivity
HcB
Maximum Energy Product
（BH)max
Temperature Coefficient　α（Br） Temperature Coefficient　α（HcJ）

Relative Recoil Permeability

μ rec

Maximum Working Temperature Density
ρ
kGs T kOe kA/m kOe kA/m MGOe kJ/m3 %/°C %/°C °C g/cm3
Max. Min. Max. Min. Min. Min. Min. Min. Max. Min. Max. Min. Typ. Typ. Typ. （L/D=0.7）Typ. Typ.
55N 14.7 1.47 11 876 10.5 836 52 414 -0.100 -0.75 1.05 80 7.50
53N 15.0 14.4 1.50 1.44 11 876 10.5 836 54 50 430 398 -0.100 -0.75
50N 14.6 14.0 1.46 1.40 11 876 10.5 836 51 47 406 374 -0.100 -0.75
48N 14.3 13.7 1.43 1.37 11 876 10.5 836 49 45 390 358 -0.100 -0.75
52M 14.8 14.2 1.48 1.42 14 1114 13.2 1051 53 49 422 390 -0.100 -0.65 100
50M 14.6 14.0 1.46 1.40 14 1114 13.1 1043 51 47 406 374 -0.100 -0.65
48M 14.3 13.7 1.43 1.37 14 1114 12.8 1019 49 45 390 358 -0.105 -0.65
50H 14.6 14.0 1.46 1.40 16 1274 13.1 1043 51 47 406 374 -0.105 -0.55 120
48H 14.3 13.7 1.43 1.37 16 1274 12.8 1019 49 45 390 358 -0.105 -0.55
46H 13.9 13.3 1.39 1.33 17 1353 12.5 995 47 43 374 342 -0.105 -0.55
44H 13.6 13.0 1.36 1.30 17 1353 12.2 971 45 41 358 326 -0.105 -0.55
42H 13.5 12.9 1.34 1.28 17 1353 12.1 963 44 40 350 318 -0.105 -0.55
40H 13.2 12.6 1.32 1.26 17 1353 11.8 939 42 38 334 302 -0.105 -0.55
48SH 14.3 13.7 1.43 1.37 20 1592 12.8 1019 49 45 390 358 -0.105 -0.55 150 7.55
46SH 13.9 13.3 1.39 1.33 20 1592 12.5 995 47 43 374 342 -0.105 -0.55
44SH 13.5 13.0 1.36 1.30 20 1592 12.2 971 45 41 358 326 -0.105 -0.55
42SH 13.5 12.9 1.35 1.29 20 1592 12.1 963 44 40 350 318 -0.105 -0.55
40SH 13.2 12.6 1.32 1.26 20 1592 11.8 939 42 38 334 308 -0.105 -0.55
38SH 12.9 12.2 1.29 1.22 20 1592 11.4 907 40 36 318 287 -0.105 -0.55
44UH 13.6 13.0 1.36 1.30 25 1990 12.2 971 45 41 358 326 -0.110 -0.50 180
42UH 13.5 12.9 1.35 1.29 25 1990 12.1 963 44 40 350 318 -0.110 -0.50
40UH 13.2 12.6 1.32 1.26 25 1990 11.8 939 42 38 334 302 -0.110 -0.50
38UH 12.9 12.2 1.29 1.22 25 1990 11.4 907 40 36 318 287 -0.110 -0.50
40EH 13.2 12.6 1.32 1.26 30 2388 11.8 939 42 38 334 302 -0.110 -0.50 200 7.60
38EH 12.9 12.2 1.29 1.22

30

2388 11.5 915 40 36 318 287 -0.110 -0.50
35EH 12.4 11.7 1.24 1.17 30 2388 10.9 868 37 33 295 263 -0.110 -0.50
33EH 12.1 11.4 1.21 1.14 30 2388 10.7 852 35 31 279 247 -0.110 -0.50
35AH 12.4 11.7 1.24 1.17 35 2786 10.9 868 37 33 295 263 -0.115 -0.45 230
33AH 12.1 11.4 1.21 1.14 35 2786 10.7 852 35 31 279 247 -0.115 -0.45
30AH 11.5 10.8 1.15 1.08 35 2786 10.1 804 32 28 255 223 -0.115 -0.45
28ZH 11.1 10.4 1.11 1.04 40 3184 9.7 772 30 26 239 207 -0.115 -0.45 250
• 1. As magnetic property might be changed by dimensions and/or shapes, some magnet design might not refer to the above property.
• 2. Temperature range to determine the temperature coefficient: ΔT: 20℃～80℃ for N grades; ΔT: 20℃～100℃ for M grades; ΔT: 20℃～120℃ for H grades; ΔT: 20℃～150℃ for SH grades; ΔT: 20℃～180℃ for UH grades; ΔT: 20℃～200℃ for EH grades; ΔT: 20℃～230℃ for AH grades; ΔT: 20℃～250℃ for ZH grades.

THRED Magnets

Br
Coercivity
HcJ
Coercivity
HcB
Maximum Energy Product
（BH)max
Temperature Coefficient　α（Br） Temperature Coefficient　α（HcJ）

Relative Recoil Permeability

μ rec

Maximum Working Temperature Density
ρ
kGs T kOe kA/m kOe kA/m MGOe kJ/m3 %/°C %/°C °C g/cm3
Max. Min. Max. Min. Min. Min. Min. Min. Max. Min. Max. Min. Typ. Typ. Typ. （L/D=0.7）Typ. Typ.
G54SH 14.4 1.44 22 1751 13.5 1075 50 398 -0.105 -0.55 1.05 150 7.50
G52SH 14.8 14.2 1.48 1.45 22 1751 13.3 1059 53 49 422 390 -0.105 -0.55
G50SH 14.6 14.0 1.46 1.40 22 1751 13.1 1043 51 47 486 374 -0.105 -0.55
G48SH 14.3 13.7 1.43 1.37 22 1751 12.8 1019 49 45 390 358 -0.105 -0.55
G46SH 13.9 13.3 1.39 1.33 22 1751 12.5 995 47 43 374 342 -0.105 -0.55
G44SH 13.6 13.0 1.36 1.30 22 1751 12.2 971 45 41 358 326 -0.105 -0.55
G50UH 14.6 14.0 1.46 1.40 25 1990 13.1 1043 51 47 406 374 -0.110 -0.50 180 7.55
G48UH 14.3 13.7 1.43 1.37 25 1990 12.8 1019 49 45 390 358 -0.110 -0.50
G46UH 13.9 13.3 1.39 1.33 25 1990 12.5 995 47 43 374 342 -0.110 -0.50
G44UH 13.6 13.0 1.36 1.30 25 1990 12.2 971 45 41 358 326 -0.110 -0.50
G42UH 13.5 12.9 1.35 1.29 25 1990 12.1 963 44 40 350 318 -0.110 -0.50
G40UH 13.2 12.6 1.32 1.26 25 1990 11.8 939 42 38 334 302 -0.110 -0.50
G48EH 14.3 13.7 1.43 1.37 30 2388 12.8 1019 49 45 390 358 -0.110 -0.50 200 7.55
G46EH 13.9 13.3 1.39 1.33 30 2388 12.5 995 47 43 374 342 -0.110 -0.50
G44EH 13.6 13.0 1.36 1.30 30 2388 12.2 971 45 41 358 326 -0.110 -0.50
G42EH 13.5 12.9 1.35 1.29 30 2388 12.1 963 44 40 350 318 -0.110 -0.50
G40EH 13.2 12.6 1.32 1.26 30 2388 11.8 939 42 38

334

302 -0.110 -0.50
G38EH 12.9 12.2 1.29 1.22 30 2388 11.5 915 40 36 318 287 -0.110 -0.50
G35EH 12.4 11.7 1.24 1.17 30 2388 10.9 868 37 33 295 263 -0.110 -0.50
G44AH 13.6 13.0 1.36 1.30 35 2786 12.2 971 45 41 358 326 -0.115 -0.45 230 7.60
G42AH 13.5 12.9 1.35 1.29 35 2786 12.1 963 44 40 350 318 -0.115 -0.45
G40AH 13.2 12.6 1.32 1.26 35 2786 11.8 939 42 38 334 302 -0.115 -0.45
G38AH 12.9 12.2 1.29 1.22 35 2786 11.5 915 40 36 318 287 -0.115 -0.45
G35AH 12.4 11.7 1.24 1.17 35 2786 10.9 868 37 33 295 263 -0.115 -0.45
G33AH 12.4 11.4 1.21 1.14 35 2786 10.7 852 35 31 279 247 -0.115 -0.45
G30AH 11.5 10.8 1.15 1.08 35 2786 10.1 804 32 28 255 223 -0.115 -0.45
G28ZH 11.1 10.4 1.11 1.04 40 3184 9.7 772 30 26 239 207 -0.115 -0.45 250 7.60

As magnetic property might be changed by dimensions and/or shapes, some magnet design might not refer to the above property.

### Thermal characteristics

 Types of NdFeB materials Thermal expansion COEFF. Maximum operating temperature Curie temperature Thermal conductivity ％/℃ °C（°F） °C（°F） Kilocalorie/ MH-℃， Ñ -0.12 176°F（80℃） 590°F（310℃） 7.7 NM -0.12 212°F（100℃） 644°F（340°C） 7.7 NH -0.11 248°F（120℃） 644°F（340°C） 7.7 NSH -0.10 302°F（150℃） 644°F（340°C） 7.7 NUH -0.10 356°F（180℃） 662°F（350℃） 7.7 NEH -0.10 392°F（200℃） 662°F（350℃） 7.7

The thermal properties listed above are usually the value class or material associated with each magnet.

### Physical and mechanical properties

 Density 7.4-7.5 g/cm3 Compressive strength 110 kg/mm2 Bending strength 25 kg/mm2 Vickers hardness (HV) 560-600 Tensile strength 7.5 kg/mm2 Yang’s modulus 1.7×104 kg/mm2 Recovery permeability 1.05μrec Resistance (R) 160μ-Ohm-cm Heat capacity 350-500 joule/（kg.℃） Coefficient of thermal expansion (0 ~ 100 ° C) Parallel magnetization direction 5.2×10 -6 /℃ Coefficient of thermal expansion (0 ~ 100 ° C) Vertical magnetization direction -0.8×10 -6 /℃

### Electroplating characteristics

 Electroplating type Overall thickness Salt spray test Pressure cooker test NiCuNi (nickel copper nickel) 15-21 micron 24 hours 48 hours Copper nickel sulfide + black nickel 15-21 micron 24 hours 48 hours NiCuNi + Gutta percha 20-28 micron 48 hours 72 hours NiCuNi + Gold 16-23 micron 36 hours 72 hours NiCuNi + Silver 16-23 micron 24 hours 48 hours Zinc 7-15 micron 12 hours 24 hours

Each layer of nickel and copper is 5-7 microns thick. The electrodeposited layer of gold and silver is 1-2 microns thick.
The test results are displayed for comparison between plating options. Your application performance may vary under your specific test conditions. The salt spray test was carried out with 5% NaCl solution at 35 ℃. The pressure cooking test (PCT) was conducted at 2 atmospheres, 120 ℃, 100% RH.

 Unit of Measure and Conversion Factors Unit Symbol cgs System SI System English System Flux Ø Maxwel weber Maxwell Flux Density B Gauss Tesla lines/in2 Magnetomotive Force F gilbert ampere turn ampere turn Magnetizing Force H Oersted ampere turns/m ampere turns/in Length L cm m in Permeability of a vacuum μν 1 0.4π x 10.6 3.192
 Conversion Factors Multiply By To Obtain inches 2.54 centimeters lines/in2 .155 Gauss lines/in2 1.55 x 105 Tesla Gauss 6.45 lines/in2 Gauss 10.4 Tesla Gilberts 0.79577 ampere turns Oersteds 79.577 ampere turns/m Ampere turns 0.4π Gilberts Ampere turns/in 0.495 Oersteds Ampere turns/in 39.37 Ampere turns/m
 Quantity Symbol Gaussian & cgs emu a Conversion factor, C b SI & rationalized mks c Magnetic flux density, magnetic induction B gauss (G) d 10-4 tesla (T), Wb/m2 Magnetic flux Φ maxwell (Mx), Gּcm2 10-8 weber (Wb), volt second (Vּs) Magnetic potential difference,magnetomotive force U, F gilbert (Gb) 10/4π ampere (A) Magnetic field strength, magnetizing force H oersted (Oe),e Gb/cm 103/4π A/m f (Volume) magnetization g M emu/cm3 h 103 A/m (Volume) magnetization 4πM G 103/4π A/m Magnetic polarization, intensity of magnetization J, I emu/cm3 4π x 10-4 T, Wb/m2 i (Mass) magnetization σ, M emu/g 1 4π x 10-7 Aּm2/kg Wbּm/kg Magnetic moment m emu, erg/G 10-3 Aּm2, joule per tesla (J/T) Magnetic dipole moment j emu, erg/G 4π x 10-10 Wbּm i (Volume) susceptibility χ, κ dimensionless, emu/cm3 4π (4π)2 x 10-7 dimensionless henry per meter (H/m), Wb/(Aּm) (Mass) susceptibility χρ, κρ cm3/g, emu/g 4π x 10-3 (4π)2 x 10-10 m3/kg Hּm2/kg (Molar) susceptibility χm, κmol cm3/mol, emu/mol 4π x 10-6 (4π)2 x 10-13 m3/mol Hּm2/mol Permeability μ dimensionless 4π x 10-7 H/m, Wb/(Aּm) Relative permeability j μr not defined – dimensionless (Volume) energy density, energy product k W erg/cm3 10-1 J/m3 Demagnetization factor D, N dimensionless 1/4π dimensionless a. Gaussian units and cgs emu are the same for magnetic properties. The defining relation is B = H + 4πM. b. Multiply a number in Gaussian units by C to convert it to SI (e.g., 1 G x 10-4 T/G = 10-4 T). c. SI (Système International d’Unitès) has been adopted by the National Bureau of Standards.Where to conversion factors are given, the upper one is recognized under, or consistent with, SI and is based on the definition B = μo(H + M), where μo = 4π x 10-7 H/m. The lower one is not recognized under SI and is based on the definition B = μoH + J, where the symbol I is often used in place of J. d. 1 gauss = 105 gamma (γ). e. Both oersted and gauss are expressed as cm-1/2ּg1/2ּs-1 in terms of base units. f. A/m was often expressed as “ampere-turn per meter” when used for magnetic field strength. g. Magnetic moment per unit volume. h. The designation “emu” is not a unit. i. Recognized under SI, even though based on the defition B = μoH + J. See footnote c. j. μr = μ/μo = 1 + χ, all in SI. μr is equal to Gaussian μ. k. BּH and μoMּH have SI units J/m3; MּH and BּH/4π have Gaussian units erg/cm3.

### Grain boundary diffusion technology

Grain boundary diffusion technology Can reduce the use volume of the rare earth (dysprosium /terbium) so that it can save the heavy rare earth resource effectively, and decreases the production cost of the magnet as well as enhance the comprehensive cost performance of high grade neodymium magnet.

Aiming at the magnets with same grade, compared with traditional technology, GBD technology uses less (HREE) Heavy rare earth and this technology can make the magnet with higher comprehensive cost performance, like 52SH, 52UH, 45EH, 42AH, 38TH, part of them Hcj(kOe)+(BH)max(MGOe)＞82.

## Samarium cobalt magnet

Samarium cobalt magnet is a kind of rare earth magnet. It is a kind of magnetic tool material which is made of samarium, cobalt and other rare earth metal materials by mixing, melting into alloy, crushing, pressing and sintering.
SmCo magnets have high magnetic energy product and very low temperature coefficient. The maximum working temperature can reach 350 ℃, and the negative temperature is unlimited. When the working temperature is above 180 ℃, the maximum magnetic energy product (BHmax), coercivity, temperature stability and chemical stability of SmCo magnets are better than those of NdFeB magnets.
SmCo magnets have strong corrosion resistance and oxidation resistance, so they are widely used in aerospace, national defense and military industry, microwave devices, communication, medical equipment, instruments, meters, various magnetic transmission devices, sensors, magnetic processors, motors, magnetic cranes, etc.
The maximum energy product (BHmax) of SmCo magnets ranges from 16 mgoe to 32 mgoe, and its theoretical limit is 34 mgoe.

### Classification

The SmCo5 and Sm2Co17 magnets are composed of SmCo5 and Sm2Co17 in two ratios: SmCo5 and Sm2Co17.
The difference between SmCo5 and Sm2Co17

#### SMCO5

The magnetic energy product of SmCo5 magnetic steel is lower than that of Sm2Co17, but its machinability is better, so it is suitable for machining special shape parts.

#### SM2CO17

Sm2Co17 magnetic energy product can achieve 28mgoe, which has excellent magnetic properties and is cheaper than SmCo5.

### Characteristic

Very good coercivity.
Good temperature stability (maximum operating temperature 250 to 350 ℃, Curie temperature 700 to 800 ℃).
It is expensive and vulnerable to price fluctuations (cobalt market price sensitive).
The material is brittle, and the general shape is square and round.
Due to the high difficulty of processing, SmCo magnets with complex shapes will be more expensive.
Brittle material, easy to produce small missing angle, the appearance of the high requirements of customers with caution.

Grade Br Hcb Hcj (BH)max Tw
kGs T kOe kA/m kOe kA/m MGOe kJ/m3 ºC
XGS32H 11.0-11.5 1.10-1.15 ≥10.2 ≥812 ≥25 ≥1990 30-32 239-255 ≤350
XGS30H 10.7-11.2 1.07-1.12 ≥9.9 ≥788 28-30 223-239
XGS28H 10.4-10.9 1.04-1.09 ≥9.6 ≥764 26-28 207-223
XGS26H 10.0-10.5 1.00-1.05 ≥9.2 ≥732 24-26 191-207
XGS24H 9.7-10.2 0.97-1.02 ≥8.9 ≥708 22-24 175-191
XGS22H 9.3-9.8 0.93-0.98 ≥8.5 ≥676 20-22 159-175
XGS20H 9.0-9.5 0.90-0.95 ≥8.2 ≥653 18-20 143-159
XGS32 11.0-11.5 1.10-1.15 ≥10.0 ≥796 ≥18 ≥1433 30-32 239-255 ≤300
XGS30 10.7-11.2 1.07-1.12 ≥9.7 ≥772 28-30 223-239
XGS28 10.4-10.9 1.04-1.09 ≥9.4 ≥748 26-28 207-223
XGS26 10.0-10.5 1.00-1.05 ≥9.0 ≥716 24-26 191-207
XGS24 9.7-10.2 0.97-1.02 ≥8.7 ≥692 22-24 175-191
XGS22 9.3-9.8 0.93-0.98 ≥8.3 ≥660 20-22 159-175
XGS20 9.0-9.5 0.90-0.95 ≥8.0 ≥637 18-20 143-159
XGS32M 11.0-11.5 1.10-1.15 ≥9.0 ≥716 ≥12 ≥955 30-32 239-255 ≤300
XGS30M 10.7-11.2 1.07-1.12 ≥8.7 ≥692 28-30 223-239
XGS28M 10.4-10.9 1.04-1.09 ≥8.5 ≥676 26-28 207-223
XGS26M 10.0-10.5 1.00-1.05 ≥8.5 ≥676 24-26 191-207
XGS24M 9.7-10.2 0.97-1.02 ≥8.5 ≥676 22-24 175-191
XGS22M 9.3-9.8 0.93-0.98 ≥8.2 ≥653 20-22 159-175
XGS20M 9.0-9.5 0.90-0.95 ≥8.0 ≥637 18-20 143-159
XGS32L 11.0-11.5 1.10-1.15 ≥6.8 ≥541 ≥8 ≥636 30-32 239-255 ≤250
XGS30L 10.7-11.2 1.07-1.12 ≥6.8 ≥541 28-30 223-239
XGS28L 10.4-10.9 1.04-1.09 ≥6.6 ≥525 26-28 207-223
XGS26L 10.0-10.5 1.00-1.05 ≥6.6 ≥525 24-26 191-207
XGS24L 9.7-10.2 0.97-1.02 ≥6.5 ≥517 22-24 175-191
XGS22L 9.3-9.8 0.93-0.98 ≥6.5 ≥517 20-22 159-175
XGS20L 9.0-9.5 0.90-0.95 ≥6.5 ≥517 18-20 143-159
XGS24LT 9.7-10.2 0.97-1.02 ≥8.7 ≥692 ≥18 ≥1433 22-24 175-191 ≤300
XGS22LT 9.3-9.8 0.93-0.98 ≥8.3 ≥660 20-22 159-175
XGS20LT 9.0-9.5 0.90-0.95 ≥8.0 ≥637 18-20 143-159
XGS18LT 8.5-9.0 0.85-0.90 ≥7.5 ≥597 16-18 127-143
XGS16LT 8.0-8.5 0.80-0.85 ≥7.0 ≥557 14-16 111-127
XGS14LT 7.5-8.0 0.75-0.80 ≥6.5 ≥517 12-14 95-111
XG24H 9.7-10.2 0.97-1.02 ≥9.2 ≥730 ≥23 ≥1830 22-24 175-191 ≤250
XG22H 9.3-9.8 0.93-0.98 ≥8.8 ≥700 20-22 159-175
XG20H 9.0-9.5 0.90-0.95 ≥8.5 ≥676 18-20 143-159
XG18H 8.5-9.0 0.85-0.90 ≥8.2 ≥653 16-18 127-143
XG16H 8.0-8.5 0.80-0.85 ≥7.8 ≥620 14-16 111-127
XG24 9.7-10.2 0.97-1.02 ≥9.2 ≥730 ≥15 ≥1194 22-24 175-191 ≤250
XG22 9.3-9.8 0.93-0.98 ≥8.8 ≥700 20-22 159-175
XG20 9.0-9.5 0.90-0.95 ≥8.5 ≥676 18-20 143-159
XG18 8.5-9.0 0.85-0.90 ≥8.2 ≥653 16-18 127-143
XG16 8.0-8.5 0.80-0.85 ≥7.8 ≥620 14-16 111-127

Note:

• The data in the above table were samples’ results tested at the temperature of 20 °C.
• The prefixes XGS and XG are for Sm2Co17 and SmCo5 magnets, respectively.
• The typical temperature coefficients of Br and Hcj are α(Br): -0.03~-0.05 %/ºC and β(Hcj): -0.20~-0.30 %/ºC, respectively.
• The suffix LT means low/near-zero temperature coefficient of Br (α(Br): +0.01 ~ -0.03 %/°C).
• The above data are only for reference, magnets can be tailored according to customers’ personalized requirements.

### Sintered SmCo Magnets’ shapes, Magnetization Direction and Size Range

 Shape Graphic Description Magnetization Direction Size Range Disc/Cylinder Magnet Axially Magnetized D: 1-100 mm T: 0.5-100 mm Diametrically Magnetized D: 1-100 mm T: 0.5-100 mm Ring Magnet Axially Magnetized OD: 5-100 mm ID: 1-90 mm T: 1-60 mm Diametrically Magnetized OD: 5-100 mm ID: 1-90 mm T: 1-60 mm Block/Rectangular Magnet Thickness Magnetized L: 1-160 mm W: 1-100 mm T: 1-100 mm Arc/Segment Magnet Diametrically Magnetized OD-ID≥1 mm L: 1-120 mm W: 3-100 mm H: 1-60 mm

NoteOther shapes of sintered SmCo magnets can also be tailored according to customers’ specific requirements.

## Bonded NdFeB magnets

Bonded neodymium iron boron magnets, are those permanent magnetic materials made of rapid quenched NdFeB magnetic powders combined with resin binders (epoxy, Nylon/polyamide (PA), polyphenylene sulfide (PPS), etc). They are manufactured through a bonded process (compression, injection, extrusion or calendaring molding), so it is available to obtain complex geometries with high dimensional precision. Controlling the performance and proportion of NdFeB magnetic powders, it is able to adjust the magnets’ magnetic properties in a continuous range. Due to their complex geometries availability, high dimensional precision, uniform magnetic properties, diverse magnetization patterns, good corrosion resistance and mechanic properties, bonded NdFeB magnets are widely applied in spindle motors, micro motors, direct current (DC) motors, synchronous motors, power tools, magnetic rollers, Hall effect sensors, etc.

### Grades of Bonded NdFeB Magnets

Grade Br Hcb Hcj (BH)max Tw
kGs T kOe kA/m kOe kA/m MGOe kJ/m3
HGT-12 7.0-7.6 0.70-0.76 5.7-6.2 454-493 8-11 637-875 10.0-11.5 80-92 ≤150
HGT-11 6.8-7.3 0.68-0.73 5.6-6.0 446-477 8-11 637-875 9.5-10.5 76-84 ≤150
HGT-10H 6.4-6.9 0.64-0.69 5.5-5.9 438-469 10-13 796-1035 9.0-10.0 72-80 ≤180
HGT-10 6.6-7.2 0.66-0.72 5.4-6.0 430-477 8-10 637-796 9.5-10.5 76-84 ≤160
HGT-9 6.3-6.9 0.63-0.69 5.2-5.8 414-462 8-10 637-796 8.5-9.5 68-76 ≤160
HGT-8H 6.0-6.6 0.60-0.66 5.0-5.6 398-446 10-13 796-1035 8-9 64-72 ≤180
HGT-8 5.8-6.4 0.58-0.64 4.8-5.4 382-430 8-10 637-796 7.5-8.5 60-68 ≤160
HGT-7 5.3-5.9 0.53-0.59 4.6-5.2 366-414 8-10 637-796 6.5-7.5 52-60 ≤160
HGT-6 4.8-5.4 0.48-0.54 4.4-5.0 350-398 8-10 637-796 5.5-6.5 44-52 ≤160
HGT-5 4.3-4.9 0.43-0.49 4.0-4.6 318-366 7-9 557-716 4.5-5.5 36-44 ≤150
HGT-4 3.8-4.4 0.38-0.44 3.5-4.2 279-334 7-9 557-716 3.5-4.5 28-36 ≤150
HGT-3 3.4-4.0 0.34-0.40 3.2-3.8 255-302 7-9 557-716 2.5-3.5 20-28 ≤150
HGT-2 3.0-3.6 0.30-0.36 2.8-3.6 223-286 7-9 557-716 2-3 16-24 ≤150

Note:

• The data in the above table were samples’ results tested at the temperature of 20 °C.

• The temperature coefficients of Br and Hcj are α(Br): -0.10~-0.13 %/ºC and β(Hcj): -0.40~-0.60 %/ºC, respectively.

• The above data are only for reference, magnets can be tailored according to customers’ personalized requirements.

### Physical Properties of Bonded NdFeB Magnets

Parameter Unit Value
Density (ρ) g/cm3 4.0-6.5
Curie Temperature (Tc) ºC 300-350
Recoil Permeability (μrec) 1.20
Rockwell Hardness (HR) MPa 35-45
Compressive Strenght (σbc) MPa 800-1000
Tensile Strength (σb) MPa 200
Thermal Expansivity (α) 10-6/ºC 1-2

Note:

• The above data are only for reference, specific magnets maybe have different values.

## Ferrite permanent magnet

Ferrite permanent magnet is made from SRO or Bao and Fe2O3 by sintering ceramic process. Because the raw materials are cheap and the production process is relatively simple, the finished product price is relatively low compared with other magnets. The main raw material of ferrite magnet is oxide, so it is not corroded by environment or chemical substances (except strong acid), so the surface does not need electroplating treatment. Mainly used in crafts, accessories, toys, motors, loudspeakers, etc.

### Grades of sintered permanent ferrite magnets

 Grade Remanence (Br) Magnetic coercivity (HcB) Intrinsic coercivity (HcJ) Maximum magnetic energy product (BH)max mT KGauss KA/m KOe KA/m KOe KJ/m3 MGOe Y8T 200~235 2.0~2.35 125-160 1.57-2.01 210-280 2.64-3.51 6.5-9.5 0.8-1.2 Y22H 310~360 3.10~3.60 220-250 2.76-3.14 280-320 3.51-4.02 20.0-24.0 2.5-3.0 Y25 360~400 3.60~4.00 135-170 1.70-2.14 140-200 1.76-2.51 22.5-28.0 2.8-3.5 Y26H-1 360~390 3.60~3.90 200-250 2.51-3.14 225-255 2.83-3.20 23.0-28.0 2.9-3.5 Y26H-2 360~380 3.60~3.80 263-288 3.30-3.62 318-350 3.99-4.40 24.0-28.0 3.0-3.5 Y27H 350~380 3.50~3.80 225-240 2.83-3.01 235-260 2.95-3.27 25.0-29.0 3.1-3.6 Y28 370~400 3.70~4.00 175-210 2.20-3.64 180-220 2.26-2.76 26.0-30.0 3.3-3.8 Y28H-1 380~400 3.80~4.00 240-260 3.01-3.27 250-280 3.14-3.52 27.0-30.0 3.4-3.8 Y28H-2 360~380 3.60~3.80 271-295 3.40-3.70 382-405 4.80-5.08 26.0-30.0 3.3-3.8 Y30H-1 380~400 3.80~4.00 230-275 2.89-3.46 235-290 2.95-3.64 27.0-32.5 3.4-4.1 Y30H-2 395~415 3.95~4.15 275-300 3.45-3.77 310-335 3.89-4.20 27.0-32.0 3.4-4.0 Y32 400~420 4.00~4.20 160-190 2.01-2.39 165-195 2.07-2.45 30.0-33.5 3.8-4.2 Y32H-1 400~420 4.00~4.20 190-230 2.39-2.89 230-250 2.89-3.14 31.5-35.0 3.9-4.4 Y32H-2 400~440 4.00~4.40 224-240 2.81-3.01 230-250 2.89-3.14 31.0-34.0 3.9-4.3 Y33 410~430 4.10~4.30 220-250 2.76-3.14 225-255 2.83-3.20 31.5-35.0 3.9-4.4 Y33H 410~430 4.10~4.30 250-270 3.14-3.39 250-275 3.14-3.45 31.5-35.0 3.9-4.4 Y34 420~440 4.20~4.40 200-230 2.51-2.89 205-235 2.57-2.95 32.5-36.0 4.1-4.4 Y35 430~450 4.30~4.50 215-239 2.70-3.00 217-241 2.73-3.03 33.1-38.2 4.1-4.8 Y36 430~450 4.30~4.50 247-271 3.10-3.40 250-274 3.14-3.44 35.1-38.3 4.4-4.8 Y38 440~460 4.40~4.60 285-305 3.58-3.83 294-310 3.69-3.89 36.6-40.6 4.6-5.1 Y40 440~460 4.40~4.60 330-354 4.15-4.45 340-360 4.27-4.52 37.6-41.8 4.7-5.2

## Shape of magnet assembly

 Circular Square Ring Counterbore Tile shape Special-shaped

## Magnetization direction

Circular magnets are divided into axial and radial magnetization; square magnets are defined in three dimensions. We define the thickness dimension along the magnetization axis. Thickness is usually the smallest size, but not always! Sometimes, the longer side is used as the magnetization direction, but we still call the longer side thickness, but the longer number is usually placed at the last number. In this way, it is easy to see the magnetization direction of the square magnet at a glance. For example, F8 * 5 * 20, the magnetization direction is 20. In addition, there are four kinds of tile magnets.

Source: China Permanent Magnet Manufacturer – www.rizinia.com