Origin of enhanced magnetoresistance of magnetic multilayers: Spin-dependent scattering from magnetic interface states

The origin of giant magnetoresistance exhibited by ferromagnetic/nonmagnetic multilayered structures is examined by inserting thin layers of a second ferromagnetic material at the interfaces in ferromagnetic/nonmagnetic/ferromagnetic sandwiches. It is generally observed, for many different combinations of metals, that the magnetoresistance depends exponentially on the thickness of the interface layer, with a characteristic length, ξ. ξ is extremely short and is typically just 1.5 to 3 at room temperature. At lower temperatures ξ becomes even shorter. The giant magnetoresistance effect is thus clearly shown to be determined by the character of the ferromagnetic/nonmagnetic interfaces. © 1993 The American Physical Society.