Observation of Exchange Interaction in Iron(II) Spin Crossover Molecules in Contact with Passivated Ferromagnetic Surface of Co/Au(111)

Spin crossover (SCO) complexes sensitively react on changes of the environment by a change in the spin of the central metallic ion making them ideal candidates for molecular spintronics. In particular, the composite of SCO complexes and ferromagnetic (FM) surfaces would allow spin-state switching of the molecules in combination with the magnetic exchange interaction to the magnetic substrate. Unfortunately, when depositing SCO complexes on ferromagnetic surfaces, spin-state switching is blocked by the relatively strong interaction between the adsorbed molecules and the surface. Here, the Fe(II) SCO complex [Fe-II(Pyrz)(2)] (Pyrz = 3,5-dimethylpyrazolylborate) with sub-monolayer thickness in contact with a passivated FM film of Co on Au(111) is studied. In this case, the molecules preserve thermal spin crossover and at the same time the high-spin species show a sizable exchange interaction of > 0.9 T with the FM Co substrate. These observations provide a feasible design strategy in fabricating SCO-FM hybrid devices.

Automated summary

Spin crossover (SCO) complexes are sensitive to changes in the environment and can change the spin of the central metallic ion, making them ideal for molecular spintronics. However, when SCO complexes are deposited on ferromagnetic surfaces, the interaction between the molecules and the surface blocks spin-state switching. This study investigates the behavior of a Fe(II) SCO complex on a passivated ferromagnetic film, showing thermal spin crossover and a sizable exchange interaction with the ferromagnetic substrate. These findings provide a feasible design strategy for SCO-ferromagnetic hybrid devices.