Introduction to Samarium Cobalt Magnets
Samarium Cobalt (SmCo) magnets are composed of samarium, cobalt and iron. These rare earth magnets are extremely strong for their small size, metallic in appearance and found in simple shapes such as rings, blocks and discs. First commercially developed in the 1970s after neodymium magnets, these advanced materials offer the best of both worlds in shielded magnet design with stable temperature performance and high magnetic output. Their unique crystalline structure enables reliable operation in extreme environments up to 350°C while maintaining corrosion resistance without surface coatings.
What Is a Samarium Cobalt Magnet?
Samarium cobalt magnets are available in two “series”: series 1:5 SmCo5 and series 2:17 Sm2Co17, both containing iron, copper and zirconium as additives. These sintered or bonded magnets create magnetic fields through aligned atomic structure, where samarium provides high magnetic anisotropy while cobalt offers thermal stability.
In contrast to neodymium magnets that fill most consumer electronics, which degrade quickly at temperatures over 80°C.
SmCo magnets are composed of samarium and cobalt, offering exceptional magnetic strength and high-temperature resistance for demanding industrial environments.
History and Development of Samarium Cobalt Magnets
The US Air Force sponsored research for temperature resistant magnetic materials led to the discovery of the first samarium-cobalt compound in 1967 at Dayton University.
A breakthrough occurred when Karl Strnat’s team showed that practical applications followed from powder metallurgy techniques transferred from the field of ceramic technology.
Commercialization gained momentum in the late 1970s in response to military programs that needed small guidance systems to operate in supersonic jet engine inlets.
| Year | History |
|---|---|
| 1966 | Sm-Co inter-metallic compound magnetic properties: theoretical prediction |
| 1969 | First sintered SmCo5 magnet produced in manufacturing quality |
| 1977 | Toshiba achieves large-scale production of Sm2(CoFeCuZr)17 |
Chemical Composition and Magnetic Properties
Samarium cobalt magnets are made of proprietary blends of samarium and cobalt that are combined into precise ratios to become these unique and strong magnetic materials. There are two main series, with approximately 15-25% samarium, broadly SmCo5 (1:5) and 2:17 types, with transition metals added to make the material structure coercive through magnetic anisotropy. Such an atomic arrangement affords excellent temperature stability while retaining high magnetic output due to large coercivity values.
Samarium Cobalt Magnet Grades and Types
The main SmCo magnet families, differing in phase structure and magnetic properties:
- 1:5 Series (SmCo5): The original 1:5 compositional series with energy products ranging from 15-24 MGOe
- 2:17 Series (Sm2Co17): Improved composition potential of 32 MGOe with the addition of iron/copper
Marine-grade 1:5 series aluminum sheets display higher corrosion resistance than other variants, and machinability is optimized compared to standard aluminum sheets. The 2:17 version is the precision choice for aerospace systems demanding the highest strength-to-size ratios.
Physical and Magnetic Characteristics
Some important properties that separate SmCo magnets from others are:
- Remanence: 8-11 kGauss range. Retains magnetism after the application field is removed
- Energy Product: Up to 32 MGOe (isotropic) – Alnico has better but less consistent values; neodymium has higher peak values
- Density: Greater mass density than NdFeB results in higher volumetric energy density in size-constrained applications
- Crystal Structure: Hexagonal lattice orientation improves intrinsic coercivity compared to isotropic magnets
Temperature Stability and Performance
SmCo retains >80% of original flux density at 300°C, contrasting with NdFeB which fails above ~150°C.
- TCurie: 500°C (1:5) – 800°C (2:17)
- TWorking Range: -50°C to 350°C depending on grade
Manufacturing Process of Samarium Cobalt Magnets
SmCo magnets are manufactured by using metallurgical methods to produce the alloy in a way which achieves final microstructure. The two main methods are: sintering used for high performance magnets or bonding for complex shapes and either influences magnetic strength, temperature resistance and dimensional control.
Material Preparation and Alloying
Adjust amount of ingredients so that raw materials including Samarium (21-23%) and Cobalt (50-65%) are weighed or the like with iron/copper/zirconium add-ons in specified ratio. To make the components, workers melt these components in an induction furnace at 1,450–1,550°C under argon-gas protection to avoid forming defects from oxidation.
The melt alloy is rapidly quenched using a water-cooled mold-casting or strip-casting method and a brittle button cast is obtained. The prepared precursor is subsequently crushed by jaw crushers to a coarse powder where particles are milled by jet milling to 3–7 microns for alignment.
Pressing, Sintering, and Machining
Powder compaction takes place in hydraulic presses, 10–15 tons force being applied while the particles are subjected to 20–35 kOe aligning fields. The best values of magnetic anisotropy have been obtained from transverse pressing as opposed to axial technique. Sintering is then carried out at 1,200–1,250°C (vacuum furnaces), resulting in particle fusing via liquid-phase diffusion.
| Process Stage | Key Parameters | Safety Measures |
|---|---|---|
| Powder Handling | Particle size ≤7µm | Nitrogen inerting systems |
| Sintering | 1250°C/2hrs vacuum | Crucible containment protocol |
The sintered blanks are subjected to diamond grinding with water-based coolants, not dry machining, because of pyrophoric risk. Tolerance (±0.05mm) requires CNC profile grinding machines. Tight tolerances (±0.05mm) require CNC profile grinding machines. Visual analysis of workpiece profile has proved to be no longer applicable due to high shape and profile accuracy requirements.
Magnetizing and Quality Control
A pulsed magnetizer excites 40–50 kOe fields through capacitor discharge systems to align magnetic domains; technicians flux verify via Helmholtz coils and crack-check by means of a fluorescent penetrant inspection facility; final products are subjected to accelerated aging tests in 300°C ambient environments; and epoxy/nickel coatings are evaluated to MIL-STD-202 salt spray standards before lot sampling confirms Br/Hci to within ±5% requirements. Batch traceability codes are laser-etched in accordance with ISO 9001 needs.
Key Benefits and Advantages of SmCo Magnets
Samarium cobalt (SmCo) magnets are well-suited for use in extreme conditions due to their high resistance to thermal conditions and corrosion, as well as their exceptional magnetic stability. These SmCo magnets are far superior to common magnets and are capable of operating in demanding environments without losing physical dimensions, making them essential for aerospace systems, precision medical equipment, and industrial automation solutions.
High Temperature Resistance and Stability
SmCo magnets maintain excellent magnetic properties at working temperatures up to 572°F (300°C), making them ideal for high-performance applications. They outperform NdFeB, Alnico, and ferrite materials due to their high maximum energy product and low temperature coefficient. Manufactured via powder metallurgy from samarium, cobalt, and rare metals, SmCo magnets exhibit maximum energy products ranging from 16 MGOe to 35 MGOe with reliable coercive force between 5,400 Oe and 22,000 Oe. Their Curie temperature reaches 800°C, with operational limits up to 350°C depending on grade:
- Grade 1: Standard (250°C)
- Grade 2: Medium (300°C)
- Grade 3: High-Temp (350°C)
- Electric vehicle motors for higher speed
- Sensors for turbine engines
- Downhole drilling equipment
Corrosion Resistance and Durability
SmCo magnets require no surface coatings due to inherent oxidation resistance, unlike neodymium alternatives. They maintain integrity in:
- Seawater immersion (marine systems)
- Chemical exposure (petrochemical processing)
- Humid environments (tropical electronics)
Comparison: Samarium Cobalt vs Neodymium Magnets
Key distinctions between leading rare-earth magnet technologies:
| Characteristic | SmCo Magnets | Neodymium Magnets |
|---|---|---|
| Max Operating Temp | 300°C | 150-220°C* |
| Corrosion Resistance | Inherent | Coating Required |
| Tensile Strength | >120 MPa | <100 MPa |
| Temp Coefficient | -0.04%/°C | -0.12%/°C |
*Specialized grades only. SmCo remains unmatched for mission-critical applications requiring minimal performance drift, while neodymium dominates cost-sensitive consumer electronics.
Common Applications of Samarium Cobalt Magnets
Samarium cobalt (SmCo) magnets are popular in applications where temperature extremes, corrosion concerns or small size are important factors: they have a consistent performance from -50 to +150 degrees C, have no risk of corrosion and are often a smaller size than an equivalent NdFeB magnet for high performance devices requiring operating stability. With the capability to offer magnetic stability from cryogenic environments up to 572°F (300°C), these are utilized throughout aerospace systems precision medical equipment industrial automation platforms where performance must not waiver.
Industrial and Commercial Uses
Robotic processing lines rely on the superior torque provided by SmCo magnets that don’t lose magnetic strength during exposure to heat for more efficient motors. Wind and hydropower systems assist in the efficient conversion of energy with SmCo permanent magnets. MRI machines operate a proven-low fail rate so physicians can be confident in their diagnosis with accurate hold of stable fields. SmCo magnetic bearings in gas and fluid metering allow assemblies to rotate with virtually no wear. Low-vibration high-speed maglev suspension applications benefit from SmCo that has been placed on the laminated pole used to make sensors.
Aerospace and Automotive Applications
Jet engine actuators are designed with SmCo magnets achieving 482°F (250°C) operating temps with no flux loss. Radiation tolerant elements make them key players in satellite positioning systems. Electric vehicle traction motors need them for dense, road-damage resistant designs. Anti-lock braking sensors include SmCo alloys because the traction strength is consistent from -40°F (-40°C) winter roads to engine bay heat. Their light weight and superb strength-to-weight ratio reduces payloads for aircraft control surfaces.
Bonded and Custom Assemblies
SmCo powder may be combined with polymers for the forming of injection-molded shapes or compression-bonded for crack-resistant, complex-shaped magnets. Applications range from housing-less sensors to high-voltage motors.
Multi-pole ring magnets may get compression-bonded to make a servo motor rotor with high volume manufacturing processes that accurately control the field pattern. Epoxy-encapsulated assemblies protect the magnet array in downhole drilling devices or assemblies designed for working in oil rig environments.
Radially magnetized geometries aid in the manufacture of linear actuators used in aircraft wing flap controls. Robotic grippers employ segmented SmCo versions to construct intense magnetic fields for handling steel plates.
Selecting the Right Samarium Cobalt Magnet
How to Choose SmCo Magnet Grades
Samarium Cobalt Magnets are available in grades from 16 to 32 MGOe (energy product) and super strong Samarium Cobalt that can even reach 35 MGOe (BHmax). High MGOe magnets (i.e., 30 or 32) offer higher magnetic output for performance critical applications but are more expensive because of higher material density needs.
In the case of high-temperature applications such as over 300°C/572°F, Sm2(CoFeCuZr)17 can be chosen as the most exemplified alloy series preferable to Sm1Co5 due to its stability. Lower-tier alternatives like SC-1615 are appropriate for budget-constrained applications with medium strength requirements.
Sizing, Tolerances, and Specifications
Standard SmCo magnets are available for disc, block, ring, and rod shapes. Magnet diameters typically range from 0.5 mm to over 100 mm depending on application, with standard tolerances around ±0.05 mm for sintered parts.
Safe Handling, Machining, and Storage Guidelines
Machining and Assembly Considerations
Samarium cobalt magnets need to be used carefully because of their extreme fragility and powerful magnetic force. Application and Processing Dry mechanical operations such as grinding or diamond wheel cutting are preferred over drilling to prevent stress fractures. Coolant should be applied in machining processes wherever possible to reduce the risk of dust formation.
During assembly:
- Attach parts to non-ferrous surfaces first before bringing magnets close to ferrous surfaces
- Use non-magnetic tools to handle small magnets
- Wear cut-resistant gloves if separating magnets
Chips more than 10% from surface loss or cracks wider than 50% across pole faces are detrimental to structural performance.
Safety Precautions and Regulatory Compliance
When dusty: use an FFP2/P2 respirator (dust mask) when the dust concentration exceeds 10mg/m³ during dust generation.
- Keep 24 inches from pacemakers/implantable devices
- Create magnetic-field-free perimeter areas for sensitive equipment
- Complies with IATA-IGC, DGR for air transport
The UK Electromagnetic Field Regulations 2016 require monitoring of field strength around high strength SmCo arrays.
Storage and Long Term Care
Preserve the magnetism by storage in:
| Condition | Temperature | Humidity |
|---|---|---|
| Requirement | -40°C to +150°C | <70% RH non-condensing |
Store magnets separated by non-conductive spacers in a closed container to prevent unintended attraction.
- Acidity/strong solvents
- Degauss with alternating field only
Surface treatments such as nickel plating improve resistance to corrosion in marine applications.
Frequently Asked Questions About Samarium Cobalt Magnets
Are Samarium Cobalt Magnets the Strongest Rare Earth Magnets?
Samarium cobalt (SmCo) magnets are another type of rare earth magnet, second in strength to neodymium. Although the magnet provides a B H Max approaching 52 MGOe compared with SmCo’s best of 32 MGOe, at elevated temperature SmCo has advantages. These magnets perform well in high heat (above 150°C or 302°F), where neodymium magnets start to demagnetize. In systems, such as aerospace systems or downhole drilling tools, that require steady magnetic output in high heat or corrosive environments, SmCo often is the preferred solution, even if max strength is slightly lower.
What Is the Typical Price Range for SmCo Magnets?
Standard grade SmCo magnets sell for about $80-150/kg depending of composition and size tolerance; usually processed by grinding or slicing. And 1:5 grade has 20% higher than 2:17 series (more cobalt) due to better temperature resistance. Specially shaped lenses that need to be diamond ground, or have special coatings applied, can jack the cost up by 35-50%. For large quantities, typically over 100 units, volume discount by manufacturer are received and complex multipole magnetizations can have setup charges.
How Do I Order Custom Samarium Cobalt Magnets?
It all starts with dimensions required magnetic orientation pattern and operating environment (found on technical datasheets or CAD files) of the magnet. Reputable manufacturers can be consulted to offer prototype services where clients verify sample batches before full production. Determine whether anisotropic (directional magnetization) or isotropic versions are imperative – the former produces a strong magnetic output at decor expense, while the latter yield greater design flexibility. Always disclose your collection to vibration frequency, levels of chemical exposure lest there are exposure risks during consultations.
