Samarium Cobalt Magnets
There are two families of Sm-Co magnets – SmCo5 and Sm2Co17. EEC Ultra High temperature magnets belong to the Sm2Co17 family.
SmCo5 was developed in the late 1960s and early 1970s. It consists of five atoms of cobalt for each samarium atom with a hexagonal crystal structure. SmCo5 magnets are also known as RECo5, Sm-Co 1:5, samarium cobalt 1:5 magnets, SmCo series 1:5 magnets, or sometimes simply 1:5 magnets.
SmCo5 has a very high intrinsic coercivity, Hci, which is a measurement of resistance to demagnetization. Its maximum energy product, (BH)max, is about 20 MGOe. The reversible temperature coefficient of residual induction of SmCo5 is about -0.04%/°C. Heavy rare earth elements, such as Gd, Tb, Ho and Er, are sometimes substituted for a portion of the Sm to reduce the reversible temperature coefficient of residual induction.
SmCo5 has very good corrosion resistance and long-term thermal stability. No surface coating is necessary. SmCo5 can be used at temperatures up to 300°C.
Sm2Co17 was developed in the 1970s. It has a rhombhedral crystal structure, which is obtained by replacing 1/3 of the Sm atoms in the SmCo5 hexagonal structure with a pair of Co atoms known as dumbbells. Commercial Sm2Co17 magnets contain other elements such as iron, copper and zirconium. The partial replacement of cobalt with iron helps increase the saturation magnetization, while the addition of copper and zirconium is critical for the formation of cellular microstructure (see figures below) for the development of high intrinsic coercivity.
Sm2Co17 is also know as RE2TM17, Sm-Co 2:17, SmCo Series 2:17, Sm(Co,Fe,Cu,Zr)z or sometimes simply 2:17 magnets.
Sm2Co17 magnets have very high intrinsic coercivity with maximum energy product (BH)max as high as 33 MGOe. Sm2Co17 magnets can be used at temperatures up to 300°C. The reversible temperature coefficient of residual induction is about -0.035%/°C. Like SmCo5 magnets, heavy rare earth elements can be substituted for a portion of the Sm in order to reduce the reversible temperature coefficient of residual induction for Sm(Co,Fe,Cu,Zr)z magnets.
Applications of Sm-Co Magnets
Sm-Co magnets are the ultimate choice for high speed motor applications due to their high resistance to demagnetization and excellent thermal stability at elevated temperatures.
Sm-Co magnets also have excellent corrosion resistance. It is not necessary to have surface coatings for most applications. It is highly desirable for demanding medical applications because of their superior corrosion resistance and thermal stability, especially when autoclave sterilization is needed for medical instruments such as surgical tools
Temperature compensated Sm-Co magnets are also the first choice for inertial devices such as gyroscopes and accelerometers, and traveling wave tubes (TWTs) due to their small reversible temperature coefficient of residual induction and excellent high temperature stability.
EEC offers Temperature Compensated (TC) specialty magnet materials with near zero reversible temperature coefficient of Br and can control the TC to the ppm level. SmCo magnets usually do not need coating to protect them from environment-induced corrosion, which allows more accurate part tolerances and simplifies use.
Magnetic Properties of Samarium Cobalt Magnets | View PDF
If you would like to see magnetic properties of customized magnet materials, please contact us.
Mechanical Properties of Samarium Cobalt Magnets | View PDF
This chart shows mechanical properties of commonly used materials. If you need specification values, please contact us.
Demagnetization Curves of Samarium Cobalt Magnets
EEC 1:5-18 | EEC 1:5-20
EEC 2:17-33 | EEC 2:17-31 | EEC 2:17-29 | EEC 2:17-27 | EEC 2:17-24 | EEC 2:17-25-T350 | EEC 2:17-24-T400 | EEC 2:17-22-T450 | EEC 2:17-20-T500 | EEC 2:17-16-T550