| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+SA+MI-TuM |
| Session: | Thin Films for Synchrotron and Magnetism Applications |
| Presenter: | Paulo Costa, University of Nebraska-Lincoln |
| Authors: | P.S. Costa, University of Nebraska-Lincoln X. Zhang, University of Nebraska-Lincoln S. Beniwal, University of Nebraska-Lincoln A.T. N'Diaye, Lawrence Berkeley National Laboratory J-F. Létard, Université de Bordeaux P.A. Dowben, University of Nebraska-Lincoln A. Enders, University of Nebraska-Lincoln |
| Correspondent: | Click to Email |
The spin crossover Fe(II) complex (SCO) of the type [Fe(H2B(pz)2)2(bipy)] has been previously shown to exhibit spin state transitions between its low spin (LS) and high spin (HS) states as a response to external stimulus such as electric fields, temperature changes, and light. It is well established that this SCO complex exhibits a crossover from its LS state to the HS state if the temperature is increased above approximately 150 K. It is demonstrated here that this spin crossover can be suppressed by mixing the SCO with strongly dipolar p-benzoquinonemonoimine zwitterion (PZI) molecules, so that unlike before, the LS state still prevails even at room temperature (RT). With the metastable LS state now locked in at RT, a spin state transition to the HS state can now be triggered optically by soft X-rays over a relatively short time of several minutes. This process is fully reversible, as cooling the mixture to 78 K has been shown to de-excite it back to its original LS state. Experiments were performed using X-ray absorption spectroscopy measurements (XAS) with synchrotron radiation tuned to the Fe L3 absorption edge as well as accompanying magnetic moment measurements taken by a superconducting quantum interference device (SQUID). The effects of temperature, photon flux, and the stoichiometric ratio between SCO and PZI in the mixture were systematically studied, and the results will be presented here. This study provides a demonstration that the spin crossover transition temperature can be tailored to create a material that exists in a meta-stable LS state at RT wherein spin states can then be switched optically.