Spin cross-over materials are built up of organo-metallic molecules that can switch between two discrete electron spin states. Graphene on top of a spin cross-over crystal is able to sense the change in spin state. This change can be read out when graphene is incorporated in a circuit, in the form of a field effect transistor. In this way, the spin crossover is reliably sensed even at long distances. The working principle of this device was confirmed by theoretical modelling of the device and the electric field generated by the crystal.
By sensing the spin cross-over point using a simple graphene device, we by-pass the need for quantum interference measurements that are conventionally required for the determination of spin transition point.