Apple has signed a $500m deal with a US firm for rare earth magnets, essential for manufacturing electronics, after China curbed exports of the scarce, vital materials. The deal, announced on Tuesday, guarantees Apple a steady flow of rare earth magnets free from China – by far the world’s largest producer. Rare earths are a group of 17 metals used to make magnets that turn power into motion, including the devices that make cellphones vibrate. Bob O’Donnell, president at market research firm TECHnalysis Research, said Tuesday’s move “makes complete sense” given that Apple requires significant amounts of rare earth magnets for its devices. MP said the deal will supply magnets for hundreds of millions of devices, which would constitute a significant share of any of Apple’s product lines.