Junctions with Ferromagnetic Electrodes

Electron transport intrinsically concerns charge and spin transfer. By breaking the spin isotropy of the nanojunction, ferromagnetic electrodes highlight the specific role played by the spin degree of freedom. We introduce the magnetic tunnel junction as the simplest reference system to interpret the transport characteristics of a spin valve. Spin interference and proximity effects are then discussed for a noninteracting resonant level model. On this basis, the specific contributions of the Coulomb interaction is examined for single and double quantum dot spin valves. Here, particular emphasis is given, respectively, to the exchange fields and the synthetic spin-orbit coupling, both arising from the interplay of electrode spin polarization and Coulomb interaction on the system. The associated precessing dynamics give raise to novel spin resonances appearing in absence of an external magnetic field, already in the sequential tunnelling regime. Moreover, proximity effects and the strong modulation of the tunnelling magnetoresistance characterizing the intermediate coupling regime are elucidated for a single spinful level and a carbon nanotube quantum dot.