Exchange-induced spin polarization in a single magnetic molecule junction

Many spintronic devices rely on the presence of spin-polarized currents at zero magnetic field.  This is often obtained by spin exchange-bias, where an element with long-range magnetic order creates magnetized states and displaces the hysteresis loop.

Here* we demonstrate that exchange-split spin states are observable and usable in the smallest conceivable unit; a single magnetic molecule.  

We use a redox-active porphyrin as a transport channel, coordinating a dysprosium-based single-molecule-magnet inside a graphene nanogap.  Single-molecule transport in magnetic field reveals the existence of exchange-split channels with different spin-polarizations that depend strongly on the field orientation, and comparison with the diamagnetic isostructural compound and milikelvin torque magnetometry unravels the role of the single-molecule anisotropy and the molecular orientation.

These results open a path to using spin-exchange in molecular electronics, and offer a method to quantify the internal spin structure of single molecules in multiple oxidation states.

*'Exchange-induced spin polarization in a single magnetic molecule junction'.