Electromotive force and huge magnetoresistance in magnetic tunnel junctions

When an electron passes through a circuit, a force will act on the charge to increase the electron's energy. This is the electromotive force (e.m.f.), and according to Faraday's law of induction, an e.m.f. cannot be induced by a static magnetic field. But there are other forces present that will act on an electron's spin, giving rise to the possibility of generating an e.m.f. of purely spin origin, even in a static magnetic field. Pham Nam Hai and colleagues have now realized such an effect using magnetic tunnel junctions containing nanoscale magnetic particles. The resulting conversion of magnetic to electrical energy in these structures gives rise to a usefully large magnetoresistive response (as high as 100,000%), and might also form the basis of a 'spin battery'.