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When to Use SmCo Instead of NdFeB Magnets?
This blog will introduce the two types of magnets: SmCo (Samarium Cobalt) and NdFeB (Neodymium Iron Boron). Both of these magnets are part of the rare-earth magnet family, renowned for their high magnetic strength. However, each magnet has specific characteristics and applications that make it better suited for different conditions. By understanding their differences, manufacturers can make more informed decisions about which magnet to use in various industrial applications.
Here, we will provide a general understanding of the properties of each magnet, how they compare, and why selecting the right one for your application can significantly affect performance, durability, and cost-effectiveness.
At Heeger Magnet, we specialize in high-quality SmCo and NdFeB magnet products, ensuring optimal performance for industrial and scientific applications.
Properties of SmCo Magnets
Samarium Cobalt magnets (SmCo) are known for their high temperature stability and resistance to corrosion. They are widely regarded as some of the most reliable and durable magnets, particularly in extreme environments.
- High Temperature Stability: SmCo magnets can operate at temperatures as high as 300°C, which makes them ideal for applications in high-temperature environments such as electric motors, aerospace, and automotive sectors.
- Corrosion Resistance: Unlike other magnetic materials, SmCo magnets are highly resistant to corrosion and oxidation, making them suitable for use in harsh environments like offshore equipment, medical devices, and marine applications.
- Long Lifespan and Durability: SmCo magnets offer excellent long-term performance and stability under stressful conditions, which is why they are often used in military and space technology.
| Property | SmCo Magnet |
| Magnetic Energy Product (BHmax) | 20 – 30 MGOe (Mega Gauss Oersteds) |
| Maximum Operating Temperature | Up to 300°C (572°F) |
| Curie Temperature (Tc) | 750°C (1382°F) |
| Residual Flux Density (Br) | 1.0 – 1.3 Tesla (10,000 – 13,000 Gauss) |
| Coercivity (Hc) | 20 – 30 kOe (kilo Oersteds) |
| Density | 8.3 – 8.5 g/cm³ |
| Magnetic Saturation (Js) | 1.1 – 1.3 Tesla (11,000 – 13,000 Gauss) |
| Bulk Modulus | 1.5 – 2.0 × 10¹¹ dynes/cm² |
| Corrosion Resistance | Excellent (does not require coating) |
| Cost | Generally higher compared to NdFeB |
| Demagnetization Resistance | Very high resistance to demagnetization |
| Max Operating Environment | Harsh conditions (marine, aerospace, etc.) |
| Weight | Heavier compared to NdFeB magnets |
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Properties of NdFeB Magnets
Neodymium Iron Boron magnets (NdFeB) are known for their high energy density and strong magnetic force. These magnets are the most commonly used rare-earth magnets in the world and are particularly sought after for their ability to produce powerful magnetic fields despite being small in size.
- High Energy Density: NdFeB magnets possess a very high magnetic energy product, which gives them an extremely strong magnetic field. They are ideal for applications where small size and powerful magnetic strength are crucial, such as in motors, headphones, and loudspeakers.
- Cost-Effectiveness: Compared to SmCo, NdFeB magnets are generally less expensive, making them a cost-effective solution for a wide range of industries.
- Versatility: These magnets are used in a wide variety of applications, including consumer electronics, electric vehicles, renewable energy systems, and medical devices.
| Property | NdFeB Magnet |
| Magnetic Energy Product (BHmax) | 30 – 55 MGOe (Mega Gauss Oersteds) |
| Maximum Operating Temperature | 80 – 200°C (176 – 392°F) |
| Curie Temperature (Tc) | 310 – 400°C (590 – 752°F) |
| Residual Flux Density (Br) | 1.0 – 1.4 Tesla (10,000 – 14,000 Gauss) |
| Coercivity (Hc) | 8 – 30 kOe (kilo Oersteds) |
| Density | 7.4 – 7.8 g/cm³ |
| Magnetic Saturation (Js) | 1.3 – 1.4 Tesla (13,000 – 14,000 Gauss) |
| Bulk Modulus | 1.4 – 1.7 × 10¹¹ dynes/cm² |
| Corrosion Resistance | Moderate (coating required) |
| Cost | Generally lower than SmCo magnets |
| Demagnetization Resistance | Moderate (sensitive to high temperatures) |
| Weight | Lighter compared to SmCo magnets |
| Magnetic Stability | Moderate, susceptible to oxidation |
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Key Differences Between SmCo and NdFeB Magnets
While both SmCo and NdFeB magnets are part of the rare-earth family, there are key differences that influence their performance in various environments.
- Temperature Tolerance: SmCo magnets can operate at much higher temperatures than NdFeB magnets. The latter typically operates in temperatures between 80°C – 200°C, while SmCo magnets can withstand temperatures as high as 300°C, which makes SmCo magnets the better choice for high-temperature applications.
- Corrosion Resistance: SmCo magnets have much better corrosion resistance compared to NdFeB magnets. NdFeB magnets typically require additional coatings, such as nickel or epoxy, to prevent corrosion, especially in moist environments.
- Magnetic Strength: NdFeB magnets have a higher magnetic energy product, which gives them stronger magnetic fields. However, they are not as durable under extreme conditions, especially high temperatures or corrosive environments.
Critical Performance Comparison
1. Magnetic Properties
| Parameter | SmCo (Grade 20) | NdFeB (N42) | Advantage |
| Remanence (Br) | 0.8-1.1 T | 1.2-1.4 T | NdFeB +30% |
| Coercivity (Hc) | 600-800 kA/m | 800-1000 kA/m | NdFeB +25% |
| Energy Product (BH)max | 20-32 MGOe | 35-55 MGOe | NdFeB +50% |
| Reversible Temp Coefficient | -0.03%/°C | -0.12%/°C | SmCo 4x better |
2. Temperature Stability
| Test Condition | SmCo Performance | NdFeB Performance |
| Max Operating Temp | 350°C (Sm₂Co₁₇) | 80-200°C (depending on grade) |
| Curie Temperature | 750-850°C | 310-400°C |
| Flux Loss at 150°C | <5% | 15-30% |
3. Corrosion Behavior
| Environment | SmCo | NdFeB (Uncoated) |
| Salt Spray Test | No corrosion after 500h | Severe rust within 24h |
| Relative Humidity | Stable at 95% RH | Requires Ni/Cu/Epoxy coating |
| Acid/Alkali Exposure | Resists pH 2-12 | Vulnerable below pH 5 |
Note: SmCo is the only choice for marine/offshore applications without protective coatings.
4. Mechanical Strength
| Property | SmCo | NdFeB |
| Vickers Hardness | 500-600 HV | 550-650 HV |
| Tensile Strength | 80-100 MPa | 70-90 MPa |
| Brittleness | Less prone to chipping | More fragile |
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When to Use SmCo Magnets?
SmCo magnets are ideal for applications that require high temperature tolerance, corrosion resistance, and long-term durability. They are best suited for extreme environments where NdFeB magnets would fail.
✔ Extreme temperatures (>200°C): Turbine sensors, downhole tools
✔ Harsh environments: Marine navigation, chemical processing
✔ Long-term stability: Aerospace systems (10- 15 yr lifespan)
| Application | SmCo Magnet |
| High-Temperature Applications | Aerospace, Motors |
| Corrosive Environments | Marine, Medical Devices |
| Military/Space Technology | Military Devices, Satellites |
When to Use NdFeB Magnets?
NdFeB magnets are ideal for applications where high magnetic strength and cost-efficiency are the primary concerns, and the environment does not subject the magnets to extreme temperatures or corrosive conditions.
✔ Cost-sensitive projects: Consumer electronics, EV motors
✔ Space-constrained designs: MRI scanners, headphones (higher Br)
✔ Non-corrosive settings: Indoor motors, magnetic separators
| Application | NdFeB Magnet |
| Cost-Effective Applications | Consumer Electronics, EVs |
| High Magnetic Force in Small Sizes | Motors, Actuators |
| General Industrial Use | Manufacturing, Robotics |
Cost Considerations
One of the main differences between SmCo and NdFeB magnets is their cost. SmCo magnets are significantly more expensive than NdFeB magnets due to the cost of the raw materials (such as samarium and cobalt). Therefore, when choosing a magnet, it’s essential to balance cost with the performance requirements of the application.
- SmCo Costs: SmCo magnets are typically more expensive due to the scarcity and cost of the raw materials.
- NdFeB Costs: NdFeB magnets are less expensive and widely available, making them a cost-effective choice for most industrial applications.
| Magnet Type | Cost | Application Fit |
| SmCo | High | High-performance, harsh environments |
| NdFeB | Moderate/Low | Cost-sensitive applications |
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FAQ
| Question | Answer |
| What is the maximum operating temperature of NdFeB magnets? | It ranges from 80°C to 200°C, with higher-temperature grades available. |
| What is the Curie temperature of NdFeB magnets? | It is between 310°C and 400°C, beyond which magnetism is lost. |
| What is the residual flux density (Br) of NdFeB magnets? | It ranges from 1.0 to 1.4 Tesla, providing strong magnetic properties. |
| How resistant are NdFeB magnets to demagnetization? | They have moderate resistance but are sensitive to high temperatures. |
| Are NdFeB magnets corrosion-resistant? | They have moderate resistance and usually require protective coatings. |
| How expensive are NdFeB magnets compared to SmCo magnets? | NdFeB magnets are less expensive due to more abundant materials and simpler production. |
In conclusion, the choice between SmCo and NdFeB magnets comes down to the specific application and environmental requirements. If you need high temperature tolerance, corrosion resistance, and long-term durability, SmCo magnets are the better choice. However, for applications requiring high magnetic strength at a lower cost, NdFeB magnets are the more cost-effective solution.
For top-quality magnetic materials, Heeger Magnet provides tailored solutions for various applications.
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