Observation of giant magnetoresistance due to open orbits in hybrid semiconductor/ferromagnet devices

We have investigated the magnetoresistance of a heterostructure containing a near surface two-dimensional electron gas subject to a periodic magnetic field that alternates in sign. The field is produced by an array of submicrometer ferromagnets fabricated on the surface of the heterostructure. We observe a giant low-field magnetoresistance due to electrons propagating in open orbits along lines of zero magnetic field. We are able to account for the observed form and magnitude of this magnetoresistance in a semiclassical model.