A samarium–cobalt (SmCo) magnet
is a type of rare earth permanent magnet made of an alloy of samarium and cobalt. They are brittle and prone to cracking and chipping. SmCo magnets are available in two "series", namely series 1:5 which has one atom of rare earth samarium and five atoms of cobalt, and series 2:17 which has two atoms of rare-earth samarium and 13–17 atoms of transition metals.