According to Faraday's law, a changing magnetic field will produce an electric field, so a static magnetic field should produce no electric field. However, Phan Nam Hai and colleagues of the University of Tokyo have noticed that there is another subtlety when electron spins are considered. In this case, the motion of a spinning electron can cause a local change in the magnetization of material and an associated Faraday-law electric field.
In suitable tunnel junctions containing MnAs quantum nanomagnets, this effect can lead to huge magnetoresistances of up to 100,000% – an effect that could lead to new magnetic sensors as well as new active devices including a "spin battery".
Further reading
Phan Nam Hai et al. 2009 Nature 458 489.