▁higher ▁co erc ivity ▁( which ▁makes ▁them ▁magnet ically ▁stable ), ▁but ▁they ▁have ▁a ▁lower ▁Cur ie ▁temperature ▁and ▁are ▁more ▁vulner able ▁to ▁ox id ation ▁than ▁sam arium – c ob alt ▁magnet s . ▁▁▁ ▁Cor ros ion ▁can ▁cause ▁un protected ▁magnet s ▁to ▁sp all ▁off ▁a ▁surface ▁layer ▁or ▁to ▁cr umble ▁into ▁a ▁pow der . ▁ ▁Use ▁of ▁protect ive ▁surface ▁treat ments ▁such ▁as ▁gold , ▁nick el , ▁z inc , ▁and ▁tin ▁pl ating ▁and ▁epo xy - res in ▁co ating ▁can ▁provide ▁cor ros ion ▁protection ; ▁the ▁majority ▁of ▁ne od ym ium ▁magnet s ▁use ▁nick el ▁pl ating ▁to ▁provide ▁a ▁robust ▁protection . ▁ ▁Origin ally , ▁the ▁high ▁cost ▁of ▁these ▁magnet s ▁limited ▁their ▁use ▁to ▁applications ▁requiring ▁compact ness ▁together ▁with ▁high ▁field ▁strength . ▁ ▁Both ▁the ▁raw ▁materials ▁and ▁the ▁pat ent ▁lic enses ▁were ▁expensive . ▁ ▁However , ▁since ▁the ▁ 1 9 9 0 s , ▁N IB ▁magnet s ▁have ▁become ▁stead ily ▁less ▁expensive , ▁and ▁their ▁lower ▁cost ▁has ▁inspired ▁new ▁uses ▁such ▁as ▁magnetic ▁construction ▁to ys . ▁ ▁Haz ards ▁ ▁The ▁greater ▁force ▁ex ert ed ▁by ▁rare - ear th ▁magnet s ▁creates ▁ha z ards ▁that ▁are ▁not ▁seen ▁with ▁other ▁types ▁of ▁magnet . ▁ ▁Mag net s ▁larger ▁than ▁a ▁few ▁cent im eters ▁are ▁strong ▁enough ▁to ▁cause ▁inj uries ▁to ▁body ▁parts ▁pin ched