In modern industrial production, permanent magnetic materials play a crucial role. Neodymium magnets and samarium cobalt (SmCo) magnets are two common types of permanent magnetic materials. They have some differences in composition, magnetic properties, and areas of application.
Structure & Composition
SmCo magnets (Sm1Co5 or Sm2Co17) and NdFeB (Nd2Fe14B) are both rare earth magnets. Samarium and neodymium are both lanthanides in the periodic table. Samarium forms an alloy with the transition metal cobalt, while neodymium forms an alloy with the transition metal iron. So each magnet results from combining a rare earth metal with a transition metal.
In terms of composition, NdFeB magnets contain 29%-32.5% neodymium, 64%-69% iron, and 1.1%-1.2% boron, with small amounts of dysprosium, terbium, niobium, copper, and other elements.
SmCo magnets, taking the 2:17 type as an example, contain 23%-28% samarium, 48%-52% cobalt, 14%-17% iron, and small amounts of copper, zirconium, and other elements.
Corrosion Resistance
SmCo magnets are composed of about 65% cobalt. Cobalt is a main component of stainless steel, which explains the excellent corrosion resistance of SmCo magnets. Cobalt is one of the three naturally ferromagnetic elements besides iron and nickel.
NdFeB magnets contain about 65% iron, which has poor corrosion resistance unless corrosion-resistant metals are added. NdFeB typically adds about 1.5% cobalt to slightly improve corrosion resistance, but this is a very small percentage compared to SmCo magnets. NdFeB magnets can be electroplated, epoxy-coated, and given other coatings for good corrosion resistance even in relatively harsh environments.
Magnetic Strength
Neodymium Iron Boron (NdFeB) is the strongest in the industry. NdFeB magnets are called the “magnetic king,” while Samarium Cobalt (SmCo) magnets have the second-highest magnetic properties.
The maximum magnetic energy product of NdFeB magnets is 52 MGOe. The BHmax of SmCo magnets is 32 MGOe.
Temperature Resistance
There are also differences in temperature resistance between NdFeB and SmCo magnets. Regular NdFeB magnets can generally reach 220°C, while Sm2Co17 can reach up to 350°C. At temperatures around 300°C, NdFeB has essentially no magnetic force, while SmCo can work normally without magnetic demagnetization.
Furthermore, the Curie temperature of NdFeB is 320°C-460°C, while for SmCo it’s 700°C-800°C. Therefore, SmCo magnets are more suitable for high-temperature applications.
Magnetic Stability
The temperature coefficient of SmCo is about 0.20-0.30%/°C, while for NdFeB it’s 0.45-0.60%/°C. This means SmCo loses less field strength per 1°C temperature increase than NdFeB.
NdFeB has a larger temperature coefficient of remanence, meaning higher temperatures result in lower remanence. SmCo has a very low-temperature coefficient of remanence, and at the same temperature, SmCo demagnetizes much less than NdFeB.
Cost
NdFeB contains a smaller proportion of rare earth elements (neodymium and boron), making it relatively cheaper. SmCo contains many rare earth elements (about 70% samarium and cobalt), making it more expensive.
Processing Characteristics
Processing characteristics are another important difference between the two types of magnets.
NdFeB magnets are more brittle and fragile during production and processing, requiring special processing methods to reduce damage.
In contrast, SmCo magnets are softer, have better processing performance, and can be more easily cut, shaped, and precisely machined.
Neodymium vs. Samarium Cobalt Magnets: Applications
NdFeB and SmCo magnets are important permanent magnetic materials with their characteristics and applications.
NdFeB magnets have the advantages of high magnetic energy product and high coercivity, widely used in electronic products, motors, and generators.
SmCo magnets have good thermal stability and corrosion resistance, with broad application prospects in high-temperature and radiation environments.
When choosing between NdFeB and SmCo magnets, it’s necessary to make a reasonable choice based on specific requirements and working environments. In high-temperature environments, SmCo magnets have an advantage; while in normal-temperature conditions requiring higher magnetic force, NdFeB magnets are more suitable.
Neodymium & Samarium Cobalt Magnets Manufacturer
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