Tunable spin-state bistability in a spin crossover molecular complex.

J Phys Condens Matter 2019 Aug 17;31(31):315401. Epub 2019 Apr 17.

Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588, United States of America.

The spin crossover (SCO) transitions at both the surface and over the entire volume of the [Fe{HB(pz)}(bipy)] polycrystalline films on AlO substrates have been studied, where pz  =  pyrazol-1-yl and bipy  =  2,2'-bipyridine. For [Fe{HB(pz)}(bipy)] films of hundreds of nm thick, magnetometry and x-ray absorption spectroscopy measurements show thermal hysteresis in the SCO transition with temperature, although the transition in bulk [Fe{HB(pz)}(bipy)] occurs in a non-hysteretic fashion at 157 K. While the size of the crystallites in those films are similar, the hysteresis becomes more prominent in thinner films, indicating a significant effect of the [Fe{HB(pz)}(bipy)]/AlO interface. Bistability of spin states, which can be inferred from the thermal hysteresis, was directly observed using temperature-dependent x-ray diffraction; the crystallites behave as spin-state domains that coexist during the transition. The difference between the spin state of molecules at the surface of the [Fe{HB(pz)}(bipy)] films and that of the molecules within the films, during the thermal cycle, indicates that both cooperative (intermolecular) effects and coordination are implicated in perturbations to the SCO transition.

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http://iopscience.iop.org/article/10.1088/1361-648X/ab1a7d
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http://dx.doi.org/10.1088/1361-648X/ab1a7dDOI Listing
August 2019
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References

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Matsumoto N et al.
J. Phys.: Conf. Ser. 2009

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