Neodymium

Nd₂Fe₁₄B, discovered independently at General Motors and Sumitomo in 1984, holds an energy product above 400 kJ/m³ — roughly ten times a ferrite magnet — and it exists because neodymium's four 4f electrons supply enormous magnetic anisotropy while the iron supplies the raw moment. Every hard-disk voice coil, every set of earbuds, every cordless-tool motor and most direct-drive wind turbines depend on it; a single 3 MW offshore turbine can carry 600 kg of the alloy. The catch is temperature: plain NdFeB starts losing its coercivity above about 80 °C, which is why dysprosium or terbium is added for anything that has to work inside a hot car. Neodymium is also the lasing ion in the Nd:YAG laser, the industrial workhorse at 1064 nm.