Rareearthtransitionmetal

Rare-earth transition metals refer to intermetallic systems in which rare earth elements are alloyed with transition metals to form compounds with notable magnetic, electronic, or catalytic properties. The term is most often encountered in the context of rare-earth permanent magnets, where lanthanoid elements such as neodymium and samarium combine with transition metals like iron or cobalt.

The most commercially important examples are Nd-Fe-B and Sm-Co magnets. Nd2Fe14B magnets, based on neodymium, iron, and boron, offer very high magnetic energy density but can be sensitive to temperature and corrosion without protective coatings. SmCo magnets, using samarium and cobalt, provide greater high-temperature stability and corrosion resistance but are typically more expensive and have lower saturation magnetization than Nd-Fe-B. Additional formulations may include praseodymium, dysprosium, or other elements to tailor performance.

Properties of these materials include high magnetic anisotropy and large coercivity, which enable strong, permanent magnetic fields in compact shapes. Their performance is highly dependent on temperature, composition, and microstructure. Processing often employs powder metallurgy, including hydrogen decrepitation, milling, alignment, compacting, sintering, and sometimes grain boundary diffusion to enhance coercivity. Surface coatings are common to mitigate corrosion, and some magnets are used in bonded or laminated form for specific applications.

Applications span demanding fields such as electric motors for wind turbines and electric vehicles, actuators, hard disk drives, speakers, and other devices requiring strong, compact magnets. Challenges include supply chain vulnerability for critical rare earth elements, environmental and geopolitical considerations, and ongoing research into recycling and substitution. See also lanthanides, transition metals, permanent magnet, NdFeB, and SmCo.