Sintered SmCo Magnets

Sintered SmCo magnets, i.e. sintered samarium cobalt magnets, are those permanent magnetic materials that based on a hexagonal crystal structure (1:5 type SmCo magnets) or a rhombohedral crystal structure (2:17 type SmCo magnets), and they are manufactured through a powder metallurgy process. They contain two basic elements samarium and cobalt. The samarium element can be substituted by a portion of other rare earth elements including praseodymium (Pr), cerium (Ce), gadolinium (Gd), erbium (Er), etc. The cobalt element can be substituted by a portion of iron (Fe) element to increase the magnets’ saturation magnetization (Ms). In order to control the microstructure and the microchemistry so as to meet required performance, it is also critical to add a small portion of copper (Cu), zirconium (Zr), titanium (Ti), etc. According to crystal structure, samarium cobalt magnets include SmCo5 magnets (1st generation of REPMs) and Sm2Co17 magnets (2nd generation of REPMs). They were invented/developed by K. Strnat’s team in the 1960s and T. Ojima’s team in the 1970s, respectively. Due to their high Curie temperature (Tc: 700-850 ºC), middle high maximum energy product ((BH)max: 110-260 kJ/m³), low temperature coefficients of remanence (α(Br): +0.01 to -0.05 %/°C) and coercivity (β(Hcj): -0.2 to -0.3 %/°C) and high corrosion resistance, sintered SmCo magnets are mainly applied in high temperature motors, servo motors, stepper/stepping motors, traveling wave tubes (TWTs), circulators, isolators, klystrons, undulators, gyroscopes, accelerometers, instruments and meters, etc.