Magneto transport on the surface of a topological insulator spin valve

The effects of the magnetization on the transport properties of a ferromagnet/barrier/ferromagnet spin valve fabricated with a topological insulator are studied. We consider two types of junctions, (i) an F1/normal barrier (NB)/F2F1/normal barrier (NB)/F2 junction and (ii) an F1/magnetic barrier (FB)/F2F1/magnetic barrier (FB)/F2 junction. The junctions in both cases lie in the xy  -plane with the magnetizations in both ferromagnetic regions, F1F1 and F2F2 aligned in the z-direction. The charge carriers in the topological insulator have a Dirac like energy spectrum of a massive relativistic particle with the magnetization M playing the role of the mass. The gap opening is a special magneto feature of topological insulators. In an anti parallel alignment of the two magnetizations, the mass of the carriers is negative in the region where M is in the negative direction. The negative mass leads the behaviors of the magneto transport properties and the tunneling magneto resistance of these junctions to be quite different from those of graphene-based spin values.