  Spin crossover (SCO) molecules are promising bi-stable magnetic switches with
applications in molecular spintronics. However, little is known about the
switching effects of a single SCO molecule when it is confined between two
metal electrodes. Here we examine the switching properties of a
[Fe(III)(EtOSalPet )(NCS)] SCO molecule that is specifically tailored for
surface deposition and binding to only one gold electrode in a nanogap device.
Temperature dependent conductivity measurements on SCO molecule containing
electromigrated gold break junctions show voltage independent telegraphic-like
switching between two resistance states at temperature below 200 K. The
transition temperature is very different from the transition temperature of 83
K that occurs in a bulk film of the same material. This indicates that the
bulk, co-operative SCO phenomenon is no longer preserved for a single molecule
and that the surface interaction drastically increases the temperature of the
SCO phenomenon. Another key finding of this work is that some devices show
switching between multiple resistance levels. We propose that in this case, two
SCO molecules are present within the nanogap with both participating in the
electronic transport and switching.
