Hysteresis and change of transition temperature in thin films of Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2}, a new sublimable spin-crossover molecule

Journal Article · Thu May 21 00:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4921309· OSTI ID:22415806

Davesne, V.; Gruber, M. ^[1]; Studniarek, M. ^[1]; Doh, W. H.; Zafeiratos, S. ^[2]; Joly, L.; Schmerber, G.; Bowen, M.; Weber, W.; Boukari, S.; Da Costa, V.; Arabski, J.; Beaurepaire, E. ^[1]; Sirotti, F.; Silly, M. G. ^[3]; Gaspar, A. B.; Real, J. A. ^[4]; others, and

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1. Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, 67034 Cedex 2 Strasbourg (France)
2. Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé, UMR 7515 CNRS, Université de Strasbourg, 25 rue Becquerel, 67087 Cedex 2 Strasbourg (France)
3. Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France)
4. Institut de Ciència Molecular (ICMol), Universitat de València, C/Catedrático José Beltrán Martínez 2, 46980 Paterna (València) (Spain)

Thin films of the spin-crossover (SCO) molecule Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2} (Fe-pyrz) were sublimed on Si/SiO{sub 2} and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen){sub 2}(NCS){sub 2}, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

• OSTI ID: 22415806
• Journal Information: Journal of Chemical Physics, Vol. 142, Issue 19; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ATOMIC FORCE MICROSCOPY
HIGH SPIN STATES
HYSTERESIS
IRON COMPOUNDS
MORPHOLOGY
NANOSTRUCTURES
PHOTOELECTRON SPECTROSCOPY
POWDERS
SILICON OXIDES
SOFT X RADIATION
SPIN
SQUID DEVICES
SUBSTRATES
TEMPERATURE RANGE 0273-0400 K
THERMODYNAMICS
THIN FILMS
TRANSITION TEMPERATURE
TRAPPING