It is strongest in substances containing paramagnetic ions such as terbium. These are aluminium, bismuth, caesium, cobalt, gold, manganese, phosphorus, scandium, sodium, terbium, and thorium. Cerium(IV) oxide has the fluorite structure, similarly to the dioxides of praseodymium and terbium. The coordination and organometallic chemistry of terbium is similar to other lanthanides. Most of the world's terbium supply is used in green phosphors. Dysprosium is one of the components of Terfenol-D, along with iron and terbium. Sodium terbium borate is used in solid state devices. A similar behavior is observed for the lanthanide analogue of berkelium, terbium. The yttrofluorite variety of the mineral fluorite owes its creamy-yellow fluorescence in part to terbium. A few coordination compounds containing terbium in its tetravalent state are also known. Terbium has no known biological role. The most common oxidation state of terbium is +3 (trivalent), such as . Yttrium and terbium are named after the village of Ytterby in Sweden. Single terbium atoms have been isolated by implanting them into fullerene molecules. Swedish chemist Carl Gustaf Mosander discovered terbium in 1843.