SmCo5

SmCo5 is an intermetallic compound consisting of samarium and cobalt with the nominal formula SmCo5. It is one of the earliest commercially used rare-earth permanent magnets and is part of the samarium–cobalt magnet family. The compound crystallizes in a hexagonal CaCu5-type structure and is typically processed as sintered magnets via powder metallurgy.

Key properties include high coercivity and excellent thermal stability, enabling retention of magnetization at elevated temperatures better than many other magnets. It also offers good corrosion resistance, particularly in oxidizing environments, and a relatively low temperature dependence of magnetization. The energy density is high for a high-temperature magnet but is generally lower than that of modern Nd2Fe14B magnets. SmCo5 magnets maintain performance over a wide temperature range, making them suitable for demanding applications.

Processing and composition: The stoichiometric composition is SmCo5, though small substitutions and grain-boundary modifications can be used to tailor properties. Production relies on powder metallurgy, producing sintered magnets; there are also bonded variants. SmCo5 magnets are relatively brittle and require protective coatings to prevent oxide formation.

Applications and history: Developed in the 1960s and commercialized in the late 1960s to 1970s, SmCo5 magnets have been used in aerospace, military, automotive, and industrial equipment where high-temperature performance and corrosion resistance are critical. They are often compared with Sm2Co17 magnets and with NdFeB magnets, offering a trade-off between energy density and temperature stability/coercivity depending on the operating environment.