Manipulation of spins at the nanoscale is one of the ultimate goals of spintronics, where new concept devices can be envisioned. We present a theoretical study of two prototypical systems, namely magnetic point contacts, and molecular spin valves. We model these systems with a combination of non-equilibrium transport techniques and electronic structure methods such as the self-consistent tight-binding model and density functional theory.
In the case of the point contacts we demonstrate that, in addition to a large magnetoresistance, asymmetries in the I-V characteristic are possible. In particular diode-like curves can arise when a domain wall is placed off-centre within the point contact, although the whole structure does not present any structural asymmetry.
In contrast magnetic spin valves are obtained by sandwiching small molecules between transition metal contacts. Also in this case the transport depends on the magnetic configuration of the contacts and typical spin-valve-like magnetoresistance behaviour is found. Interestingly for small molecules the sign of the magnetoresistance depends on the bias.