It is generally agreed that the history of rare earth permanent magnets began with the discovery by Karl Strnat in 1967 of extremely large magnetocrystalline anisotropy for YCo5. Velge and Buschow at the Phillips Research Laboratories reported producing a SmCo5 magnet with an energy product of 8.1 MGOe (64.5 kJ/m3) and an intrinsic coercivity of 5.2 kOe (413.8kA/m) in 1968. This magnet, which was produced from SmCo5 powder that was aligned and compacted in a magnetic field, appears to be the first SmCo5 magnet ever produced. General Electric Research Center was the first to produce fully dense and stable SmCo5 magnets using liquid-phase sintering technique, which became the standard process for all types of Samarium Cobalt magnets, and later for sintered Neodymium magnets. SmCo5 based magnets, also known as the first generation of rare earth magnets, with an energy product of up to 24.0 MGOe (191.1 kJ/m3), are still widely used today in many applications. Shortly after the development of SmCo5 based magnets in the early 1970’s, researchers turned their attention to the Sm2Co17 intermetallic phase. Sm2Co17 based magnets were an outgrowth of the investigation of R2(Co, Fe)17 alloys in the 1970s to increase the energy product. In the mid-1970s, research in TDK Electronics Corp. to optimize Copper (Cu) and Zirconium (Zr) content in Sm2(Co,Fe,Cu,Zr)17 alloys resulted in an energy product as high as 30.0 MGOe (239.0 kJ/m3), which led to the commercial success of the second generation of rare earth magnets.
