These are very hard and brittle. Oxidise very little in a humid atmosphere and are very resistant to water.
A Samarium-Cobalt (SmCo) magnet, a kind of rare earth magnet, is a strong permanent magnet, which consists of the two basic elements Samarium and Cobalt exists. They are available in two "series", namely SmCo5 magnets and Sm2Co17 magnets. They were developed in the early 1960s to the basis of the work of Karl Strnat and Alden Ray at the Wright-Patterson Air Force Base or the University of Dayton.
In terms of strength, they are generally classified similar to neodymium magnets, but have higher temperature values and a higher coercivity. Samarium-Cobalt magnets have maximum energy products (BHmax), which can be 14 Megagauss-Oersted (MG-Oe) to 33 MG-Oe, so about 112 kJ/m3 to 264 kJ/m3; their theoretical limit is 34 MG-Oe, about 272 kJ/m3.