TECHNICAL GUIDE
Samarium cobalt magnets represent an engineering solution of excellence whenever three key challenges need to be addressed: extreme heat, chemically aggressive environments, and the need for absolute long-term reliability. Choosing the correct SmCo grade, between SmCo5 and Sm2Co17, and carefully designing their mechanical integration can significantly improve the quality, performance, and safety of any industrial or aerospace application.
Developed from the 1970s onward, rare-earth magnets based on a Samarium-Cobalt alloy are the preferred choice for applications requiring reliability, resistance to extreme temperatures, and outstanding magnetic stability over time.
In this article, we will take an in-depth look at what Samarium Cobalt magnets are, their chemical and physical properties, the criteria for selecting them, and a detailed comparison with Neodymium magnets.
Samarium cobalt magnets belong to the family of rare-earth permanent magnets. They are primarily composed of an alloy of Samarium, a rare-earth element, and Cobalt, a transition metal, often combined with smaller percentages of iron, copper, zirconium, or hafnium to improve their magnetic and structural properties.
There are two main types of Samarium Cobalt alloys, classified according to the atomic ratio of their primary elements:
SmCo5 Series (1:5 Ratio)
This was the first generation of commercially available SmCo magnets. It consists of one Samarium atom for every five Cobalt atoms.
Its maximum energy product (BHmax) generally ranges from 15 to 22 MGOe.
They offer good magnetic stability and are easier to magnetize than the subsequent series, but they have lower magnetic strength and lower mechanical resistance.
Sm2Co17 Series (2:17 Ratio)
This represents the technological evolution of the alloy, with a crystal structure containing two Samarium atoms and seventeen Cobalt atoms, together with the addition of iron and copper.
Its maximum energy product can reach and exceed 32 MGOe.
They offer superior magnetic performance, good thermal stability, and improved corrosion resistance, although they require extremely high magnetizing fields.
To fully understand the value of these components in an industrial project, it is necessary to analyze their intrinsic properties. These magnets are selected for their resilience in demanding operating environments.
Extreme Temperature Resistance
The distinctive characteristic that makes these products unique is their classification as high-temperature magnets. While standard Neodymium magnets can begin to experience irreversible magnetic losses at temperatures as low as 80°C–100°C (except for certain specialized and more expensive grades), Samarium Cobalt magnets can operate continuously at temperatures ranging from 250°C to 350°C, with some special alloys maintaining stability up to 500°C.
Excellent Temperature Coefficient
Every magnet experiences a temporary loss of magnetic strength as temperature increases. This phenomenon is governed by the temperature coefficient of remanence (αBr). For SmCo magnets, this value is exceptionally low, at approximately -0.03% to -0.04% per degree Celsius. This means that the magnetic flux remains almost linear and stable even in the presence of significant thermal fluctuations.
Exceptional Resistance to Corrosion and Oxidation
Unlike Neodymium magnets, which contain a high percentage of iron and are highly susceptible to corrosion when exposed to moisture (and therefore generally require protective coatings), Samarium Cobalt magnets contain very little or no free iron. As a result, they offer inherent corrosion resistance, often making surface plating unnecessary.
High Coercivity and Resistance to Demagnetization
Coercivity (Hcj) measures a magnet’s ability to resist external demagnetizing fields. Thanks to their anisotropic structure, Samarium Cobalt magnets have extremely high intrinsic coercivity. They are highly resistant to demagnetization caused by reverse magnetic fields, mechanical shocks, or ionizing radiation.
One of the most common engineering dilemmas involves choosing between Samarium Cobalt vs Neodymium. Both are rare-earth magnets, but they address significantly different application requirements. Let’s compare them point by point:
| Characteristic | Neodymium Magnets (NdFeB) | Samarium Cobalt Magnets (SmCo) |
|---|---|---|
| Magnetic Strength (BHmax) | High (up to 52 MGOe and above) | High/Moderate (15 to 32 MGOe) |
| Maximum Operating Temperature | Typically 80°C (up to 200°C for special grades) | 250°C to 350°C / 500°C |
| Curie Temperature | Approximately 310°C–350°C | Approximately 700°C–800°C |
| Corrosion Resistance | Poor (protective coating generally required) | Excellent (coating rarely required) |
| Mechanical Strength | Moderate (brittle, but machinable with care) | Very brittle (prone to chipping) |
| Raw Material Cost | Fluctuating, but generally lower | High (due to the cost of Cobalt and Samarium) |
Do you need to choose between SmCo and Neodymium?
Choosing the right magnet depends on operating temperature, required magnetic field, operating environment, and design constraints.
Tell us about your application: we can help you identify the most suitable technology and SmCo specification for your requirements.
Request a Technical Consultation
Thanks to their unique technical characteristics, Samarium Cobalt magnets are used in high-tech industrial markets where component failure is not an option.
Aerospace and Defense
In space and aerospace defense systems, environmental conditions can be extreme. SmCo magnets are used in:
Automotive and Motorsport
High-performance electric motors, particularly those used in motorsport or advanced hybrid systems, generate significant heat inside the rotor. Neodymium magnets may be at risk of demagnetization under these conditions. Samarium Cobalt ensures that the motor maintains its efficiency and torque even under prolonged loads and at extremely high rotational speeds.
Industrial Sensors and Measurement Systems
Position sensors, flowmeters, and transducers operating near boilers, internal combustion engines, or high-temperature industrial processes require high-temperature magnets. The thermal stability of SmCo magnets ensures that sensor readings do not experience drift or calibration errors caused by ambient heat.
Oil & Gas Industry (Downhole Drilling)
During deep oil or geothermal drilling operations, measurement probes can descend several kilometers underground, where temperatures can easily exceed 200°C and pressures become extremely high. SmCo magnets power downhole alternators and drill orientation sensors without significant performance degradation.
Magnetic Couplings and Magnetically Driven Pumps
Used for pumping highly corrosive or toxic fluids, magnetically driven pumps eliminate the need for dynamic seals, significantly reducing the risk of leakage. Samarium Cobalt magnets ensure reliable torque transmission even with high-temperature fluids while also resisting potentially acidic or corrosive vapors.
Designing a system that incorporates Samarium Cobalt magnets requires an understanding of certain inherent limitations related to the material’s mechanical and manufacturing characteristics.
Mechanical Brittleness
Samarium Cobalt alloy is structurally very brittle and crystalline. It does not tolerate mechanical impacts, bending, or structural stress well. If allowed to collide violently with other magnets or metal surfaces, SmCo magnets can easily chip or break into fragments.
It is therefore essential to provide adequate tolerances in mounting seats and to favor fastening systems based on structural bonding, using high-temperature-resistant epoxy resins, or mechanical encapsulation rather than press-fit assemblies.
Machining and Cutting
Due to the hardness and brittleness of the material, SmCo magnets cannot be machined using conventional methods such as drilling or milling with carbide tools. Machining should be performed before final magnetization using:
Liquid cooling is essential during cutting to prevent the fine dust generated during machining, which may contain Cobalt and iron, from overheating and potentially igniting spontaneously in air.
When deciding to integrate Samarium Cobalt magnets into a production supply chain, it is essential to assess the risks associated with raw material sourcing. Unlike many other industrial components, the SmCo magnet market is strongly influenced by international geopolitical dynamics.
China effectively holds a dominant position in both the extraction and refining of rare-earth elements. Within this context of supply-chain dependence, in April 2025, the Chinese government introduced strict export licensing requirements for several rare-earth elements.
Samarium is included in the official list of rare-earth elements subject to these special export licensing requirements. This means that manufacturers and buyers may have to contend with potential administrative delays and sudden price fluctuations.
In summary, magnet selection should not be based solely on absolute magnetic strength under laboratory conditions, but rather on the actual operating conditions of the application and its duty cycle.
Samarium Cobalt magnets represent an engineering solution of excellence whenever three key challenges need to be addressed: extreme heat, chemically aggressive environments, and the need for absolute long-term reliability. Selecting the correct SmCo grade (SmCo5 vs Sm2Co17) and carefully designing its mechanical integration can significantly improve the performance, quality, and safety of any industrial or aerospace application.
When temperature, stability, and reliability are critical requirements, choosing the right SmCo magnet can make a significant difference to the performance and service life of the system.
Do you have an industrial, automotive, aerospace, or high-temperature application?
Our team is available to evaluate your application and identify the most suitable Samarium Cobalt solution, from selecting the appropriate grade to configuring the magnet.
