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Title: 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

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.
Authors:
;  [1] ;  [2] ;  [1] ;  [3] ; ;  [4] ; ; ; ; ; ; ; ;  [1] ; ;  [5] ; ;  [6] ;
  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. (Germany)
  3. (France)
  4. 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)
  5. Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette (France)
  6. Institut de Ciència Molecular (ICMol), Universitat de València, C/Catedrático José Beltrán Martínez 2, 46980 Paterna (València) (Spain)
Publication Date:
OSTI Identifier:
22415806
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 19; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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