Permanent magnets are essential components in many industrial and engineering systems, providing a stable magnetic field without the need for an external power source. To properly understand their performance and characteristics, permanent magnets are commonly classified using two key dimensions: type and grade. These classifications help describe the material composition, magnetic strength, thermal behavior, and overall performance level of a magnet.
This article provides a clear overview of the main types of permanent magnets and the commonly used grades within each type, offering a concise reference for understanding how permanent magnets are categorized.
Types of Permanent Magnets
Permanent magnet types are defined by their base material. Each material exhibits distinct magnetic and physical properties, which determine its performance range and typical use cases.
Ferrite (Ceramic) Magnets
Ferrite magnets, also known as ceramic magnets, are made from iron oxide combined with strontium or barium carbonate. They are one of the most widely used permanent magnet types due to their balanced performance and cost advantages.
Key characteristics of permanent ferrite magnets include:
- Moderate magnetic strength compared to rare-earth magnets
- Good resistance to demagnetization
- Excellent corrosion resistance without surface coating
- Stable performance over a wide temperature range
Permanent ferrite magnets are often chosen where cost efficiency and environmental stability are prioritized over maximum magnetic force.
Neodymium (NdFeB) Magnets
Neodymium magnets are rare-earth magnets composed of neodymium, iron, and boron. They offer the highest magnetic energy density among all permanent magnet materials.
Key characteristics of neodymium magnets include:
- Extremely high magnetic strength relative to size
- Compact design potential due to strong magnetic force
- Sensitivity to high temperatures
- Susceptibility to corrosion if uncoated
Because of their performance intensity, neodymium magnets are typically used when strong magnetic output is required within limited space.
Samarium Cobalt (SmCo) Magnets
Samarium cobalt magnets are another class of rare-earth magnets, known for their exceptional thermal and chemical stability.
Key characteristics of samarium cobalt magnets include:
- High resistance to demagnetization
- Excellent performance at elevated temperatures
- Strong corrosion resistance without additional coatings
- Consistent magnetic behavior under harsh conditions
Compared to neodymium magnets, SmCo magnets offer slightly lower magnetic strength but superior stability in demanding environments.
Alnico Magnets
Alnico magnets are primarily composed of aluminum, nickel, and cobalt. They were among the earliest high-performance permanent magnets developed and are still used in specialized applications.
Key characteristics of alnico magnet include:
- High maximum operating temperature
- Stable magnetic output
- Low coercivity compared to modern magnet materials
Due to their low resistance to demagnetization, alnico magnets require careful magnetic circuit design to maintain performance.
What Are Magnet Grades?
While magnet type defines the base material, magnet grade describes the performance level within that material type. Grades are standardized indicators that reflect a magnet’s magnetic strength and related properties.
In general, magnet grades are associated with:
- Maximum energy product (BHmax)
- Remanence (Br)
- Coercivity (Hc)
It is important to note that grades are material-specific. A grade number used for one magnet type does not correspond to the same performance level in another type.
Common Grades of Permanent Magnets
Common Ferrite Magnet Grades
Ferrite magnet grades are typically identified using alphanumeric designations.
Common ferrite grades include:
- Y30: Standard grade with balanced magnetic performance
- Y35: Higher magnetic strength compared to Y30
As the grade increases, ferrite magnets generally exhibit higher magnetic output, while maintaining similar corrosion resistance and temperature stability.
Related article: What Is a Ferrite Magnet? Properties, Grades, and Applications
Common Neodymium Magnet Grades
Neodymium magnet grades are commonly expressed using an “N” followed by a number, which indicates the maximum energy product.
Common standard grades include:
- N35
- N42
- N52
Higher numbers represent stronger magnetic performance. In addition, neodymium magnets often include temperature-rated suffixes:
- H – High temperature
- SH – Super high temperature
- UH – Ultra-high temperature
- EH – Extremely high temperature
For example, N42SH offers lower magnetic strength than N52 but significantly better thermal resistance.
The table below summarizes commonly used neodymium magnet grades and their typical magnetic properties.
| Grade | Br (mT / kGs) | Hcb (kA/m / kOe) | Hcj (kA/m / kOe) | (BH)max (kJ/m³ / MGOe) | Max Operating Temp (°C) |
| N35 | 1170–1220 / 11.7–12.2 | ≥ 868 / ≥ 10.9 | ≥ 955 / ≥ 12 | 263–287 / 33–36 | 80 |
| N38 | 1220–1250 / 12.2–12.5 | ≥ 899 / ≥ 11.3 | ≥ 955 / ≥ 12 | 287–310 / 36–39 | 80 |
| N40 | 1250–1280 / 12.5–12.8 | ≥ 907 / ≥ 11.4 | ≥ 955 / ≥ 12 | 302–326 / 38–41 | 80 |
| N42 | 1280–1320 / 12.8–13.2 | ≥ 915 / ≥ 11.5 | ≥ 955 / ≥ 12 | 318–342 / 40–43 | 80 |
| N48 | 1380–1420 / 13.8–14.2 | ≥ 923 / ≥ 11.6 | ≥ 955 / ≥ 12 | 366–390 / 46–49 | 80 |
| N50 | 1400–1450 / 14.0–14.5 | ≥ 796 / ≥ 10.0 | ≥ 876 / ≥ 11 | 382–406 / 48–51 | 80 |
| N52 | 1430–1480 / 14.3–14.8 | ≥ 796 / ≥ 10.0 | ≥ 876 / ≥ 11 | 398–422 / 50–53 | 80 |
| 33M | 1130–1170 / 11.3–11.7 | ≥ 836 / ≥ 10.5 | ≥ 1114 / ≥ 14 | 247–263 / 31–33 | 100 |
| 35M | 1170–1220 / 11.7–12.2 | ≥ 868 / ≥ 10.9 | ≥ 1114 / ≥ 14 | 263–287 / 33–36 | 100 |
| 38M | 1220–1250 / 12.2–12.5 | ≥ 899 / ≥ 11.3 | ≥ 1114 / ≥ 14 | 287–310 / 36–39 | 100 |
| 40M | 1250–1280 / 12.5–12.8 | ≥ 923 / ≥ 11.6 | ≥ 1114 / ≥ 14 | 302–326 / 38–41 | 100 |
| 42M | 1280–1320 / 12.8–13.2 | ≥ 955 / ≥ 12.0 | ≥ 1114 / ≥ 14 | 318–342 / 40–43 | 100 |
| 45M | 1320–1380 / 13.2–13.8 | ≥ 995 / ≥ 12.5 | ≥ 1114 / ≥ 14 | 342–366 / 43–46 | 100 |
| 48M | 1360–1430 / 13.6–14.3 | ≥ 1027 / ≥ 12.9 | ≥ 1114 / ≥ 14 | 366–390 / 46–49 | 100 |
| 50M | 1400–1450 / 14.0–14.5 | ≥ 1033 / ≥ 13.0 | ≥ 1114 / ≥ 14 | 382–406 / 48–51 | 100 |
| 35H | 1170–1220 / 11.7–12.2 | ≥ 868 / ≥ 10.9 | ≥ 1353 / ≥ 17 | 263–287 / 33–36 | 120 |
| 38H | 1220–1250 / 12.2–12.5 | ≥ 899 / ≥ 11.3 | ≥ 1353 / ≥ 17 | 287–310 / 36–39 | 120 |
| 40H | 1250–1280 / 12.5–12.8 | ≥ 923 / ≥ 11.6 | ≥ 1353 / ≥ 17 | 302–326 / 38–41 | 120 |
| 42H | 1280–1320 / 12.8–13.2 | ≥ 955 / ≥ 12.0 | ≥ 1353 / ≥ 17 | 318–342 / 40–43 | 120 |
| 45H | 1320–1360 / 13.2–13.6 | ≥ 963 / ≥ 12.1 | ≥ 1353 / ≥ 17 | 342–366 / 43–46 | 120 |
| 48H | 1370–1430 / 13.7–14.3 | ≥ 995 / ≥ 12.5 | ≥ 1353 / ≥ 17 | 366–390 / 46–49 | 120 |
| 35SH | 1170–1220 / 11.7–12.2 | ≥ 876 / ≥ 11.0 | ≥ 1592 / ≥ 20 | 263–287 / 33–36 | 150 |
| 38SH | 1220–1250 / 12.2–12.5 | ≥ 907 / ≥ 11.4 | ≥ 1592 / ≥ 20 | 287–310 / 36–39 | 150 |
| 40SH | 1240–1280 / 12.4–12.8 | ≥ 939 / ≥ 11.8 | ≥ 1592 / ≥ 20 | 302–326 / 38–41 | 150 |
| 45SH | 1320–1380 / 13.2–13.8 | ≥ 1003 / ≥ 12.6 | ≥ 1592 / ≥ 20 | 342–366 / 43–46 | 150 |
| 28UH | 1020–1080 / 10.2–10.8 | ≥ 764 / ≥ 9.6 | ≥ 1990 / ≥ 25 | 207–231 / 26–29 | 180 |
| 30UH | 1080–1130 / 10.8–11.3 | ≥ 812 / ≥ 10.2 | ≥ 1990 / ≥ 25 | 223–247 / 28–31 | 180 |
| 33UH | 1130–1170 / 11.3–11.7 | ≥ 852 / ≥ 10.7 | ≥ 1990 / ≥ 25 | 247–271 / 31–34 | 180 |
| 35UH | 1180–1220 / 11.8–12.2 | ≥ 860 / ≥ 10.8 | ≥ 1990 / ≥ 25 | 263–287 / 33–36 | 180 |
| 38UH | 1220–1250 / 12.2–12.5 | ≥ 876 / ≥ 11.0 | ≥ 1990 / ≥ 25 | 287–310 / 36–39 | 180 |
| 40UH | 1240–1280 / 12.4–12.8 | ≥ 899 / ≥ 11.3 | ≥ 1990 / ≥ 25 | 302–326 / 38–41 | 180 |
| 28EH | 1040–1090 / 10.4–10.9 | ≥ 780 / ≥ 9.8 | ≥ 2388 / ≥ 30 | 207–231 / 26–29 | 200 |
| 30EH | 1080–1130 / 10.8–11.3 | ≥ 812 / ≥ 10.2 | ≥ 2388 / ≥ 30 | 223–247 / 28–31 | 200 |
| 33EH | 1130–1170 / 11.3–11.7 | ≥ 876 / ≥ 10.5 | ≥ 2388 / ≥ 30 | 247–271 / 31–34 | 200 |
| 35EH | 1170–1220 / 11.7–12.2 | ≥ 876 / ≥ 11.0 | ≥ 2388 / ≥ 30 | 263–287 / 33–36 | 200 |
| 38EH | 1220–1250 / 12.2–12.5 | ≥ 899 / ≥ 11.3 | ≥ 2388 / ≥ 30 | 287–310 / 36–39 | 200 |
| 28AH | 1040–1090 / 10.4–10.9 | ≥ 787 / ≥ 9.9 | ≥ 2624 / ≥ 33 | 207–231 / 26–29 | 230 |
| 30AH | 1080–1130 / 10.8–11.3 | ≥ 819 / ≥ 10.3 | ≥ 2624 / ≥ 33 | 223–247 / 28–31 | 230 |
| 33AH | 1130–1170 / 11.3–11.7 | ≥ 843 / ≥ 10.6 | ≥ 2624 / ≥ 33 | 247–271 / 31–34 | 230 |
Common SmCo Magnet Grades
Samarium cobalt magnets are generally classified by material composition rather than numerical strength alone.
The two most common categories are:
- SmCo 1:5 – Good magnetic strength with excellent stability
- SmCo 2:17 – Higher energy product and improved temperature performance
SmCo grades focus primarily on long-term stability and resistance to thermal demagnetization rather than maximizing magnetic force.
Common Alnico Magnet Grades
Alnico magnet grades are identified by numerical designations that reflect composition and coercivity.
Common grades include:
- Alnico 2 – Lower coercivity and moderate magnetic strength
- Alnico 5 – Widely used grade with balanced properties
- Alnico 8 – Higher coercivity and improved resistance to demagnetization
Differences between alnico grades mainly relate to coercive force and magnetic stability rather than overall strength.
Conclusion
Permanent magnets are systematically classified by type and grade to describe their material composition and magnetic performance. Magnet type defines the fundamental properties of the material, while magnet grade specifies the performance level within that material category. Understanding these classifications provides a clear framework for comparing permanent magnets and interpreting their technical specifications.
By distinguishing between magnet types and recognizing commonly used grades, you can better evaluate magnetic materials and their performance characteristics in technical documentation and design discussions.
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