"No replacement has been found for neodymium that enhances the power of
magnets at high heat and is crucial for hard-disk drives, wind turbines,
and the electric motors of hybrid cars. Each Toyota Prius uses 25 pounds
of rare earth elements. Cerium and lanthanum are used in catalytic
converters for diesel engines. Europium is used in lasers."
Read it all,
http://www.telegraph.co.uk/finance/comment/ambroseevans_pritchard/6082464/World-faces-hi-tech-crunch-as-China-eyes-ban-on-rare-metal-exports.html