ESRF Seminar
Variable Pressure study of Prussian blue analogues by XAS and XMCD
Jean-Daniel CAFUN
SYNCHROTRON SOLEIL
| What | Seminar |
|---|---|
| When |
02-09-2010 at 15:00 |
| Where | CTRM Control Room |
| Coordinator Contact | Isabelle Combe |
| Host(s) | |
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One of the challenges in the field of molecular magnetism is the design of optically and thermally switchable magnetic materials for which various kinds of applications may be feasible. The long-known photomagnetic CoFe Prussian blue analogues (PBA) appear to have great potentials for these technological applications. In CoFe Prussian blue analogues, the photomagnetic properties are due to the CoII(HS)-FeIII ® CoIII(LS)-FeII electron transfer accompanied by the spin state change of the Co ion.[1],[2],[3] In these compounds, in spite of the considerable experimental and theoretical effort, the origin of the switchable properties remains unclear. If the oxidation and spin states of the stable and metastable states involved in the process are now well characterized, some questions remain on the atomic arrangement of the Co-NC-Fe linkages, water molecules and alkali cations in the structure and their role in the switching properties.
In the f.f.c structure of Co-Fe PBA, the alkali cations which are located around the Td sites, are in very weak interactions with the bimetallic Co-NC-Fe network.[4] These weak interactions can hardly be evidenced at room pressure. Thus variable pressure study turned out to be an appropriate technique to study tricky compounds such as PBA since variable pressure measurements have provided valuable data on interatomic forces and chemical bonding in the solid.[5] Here we present (i) the XAS study of a Co-Fe Prussian blue analogues under variable pressure which evidences a photo-induced effect in a pressure-induced state at room temperature and (ii) the XMCD study of two Ni-Fe PBA under variable pressure showing that the magnetic properties in these PBA compounds are linked to interaction between the alkali metal ions and the bimetallic Ni-NC-Fe network.[6]
The results show that variable pressure study can provide essential piece of information to establish the link between the unusual electronic properties of Co-Fe and Ni-Fe Prussian blue analogues and their structure.
ReferenceS
[1]. Sato O., Iyoda T., Fujishima A., Hashimoto K., Science, 1996, 272, 704-705.
[2]. Cartier dit Moulin C., Villain F., Bleuzen A., Arrio M.-A., Sainctavit P., Lomenech C., Escax V., Baudelet F., Dartyge E., Gallet J.J., Verdaguer M., J. Am. Chem. Soc. 2000, 122, 6653-6658.
[3]. Yokoyama T., Ohta T., Sato O., Hashimoto K., Phys. Rev B: condens. Matter. 1998, 58, 8257-8266.
[4]. Lüdi A., Güdel H. U., Structure and Bonding, Spinger-Verlag, Berlin, 1973, 1-21.
[5]. (a) Gütlich P., Gaspar A. B., Ksenofontov, V., Garcia Y., J. Phys. Condens. Matter, 2004, 1087-1108. (b) Ksenofontov, Gaspar A. B., V., Gütlich P., Top. Curr. Chem., 2004, 235, 23-64. (c) Boillot M.-L., Zarembowitch J., Itié J.-P, Polian A., Bourdet E., Haasnoot J. G., New J. Chem., 2002, 26, 313-322.
[6]. Bleuzen A., Cafun J.-D., Bachschmidt A., Verdaguer M., Munsch P., Baudelet F., Itié J.-P., J. Phys. Chem. C., 2008, 112, 17709-17715
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