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NON-LINEAR BEHAVIOUR OF THE SPIN TRANSITION COMPOUNDS DURING PHOTO-EXCITATION AND RELAXATION

C. Enachescu1,2,* , J. Linares2, E. Codjovi2, K. Boukheddaden2, F. Varret2

Affiliation

  1. ”Alexandru Ioan Cuza” University, Faculty of Physics, Iasi, Bdul Carol I, nr. 11, 6600, Romania
  2. Laboratoire de Magnétisme et d'Optique, CNRS-Université de Versailles (UMR 8634), 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France

Abstract

Spin-crossover solids are photo-excitable materials, which are studied for future applications as optical memories or numerical display. The spin transition is a first order phase transition produced by variations of temperature, pressure or light. Cooperative effects constitute the basic mechanism for the spin crossover transition. They induce instability in the thermodynamic competition between the two states of the spin-crossover molecules: high-spin (HS) and low spin (LS).We investigate here the photo-excitation process and the relaxation of the photo-excited state in photo-switchable solids, such as spin transitions systems [(FexM1-x)(btr)2(NCS)2] H2O, with M=Co, Ni, Zn. We follow the competition between the relaxation and the photo-excitation processes (up and eventually down). The experimental kinetics gives evidence for a non-linear character of the relaxation at all temperatures, including the tunnelling regime, and for non-linear behaviours of the photo-excitation rates..

Keywords

Spin transition compounds, Relaxation, Photo-excitation.

Submitted at: July 23, 2002
Accepted at: March 12, 2003

Citation

C. Enachescu, J. Linares, E. Codjovi, K. Boukheddaden, F. Varret, NON-LINEAR BEHAVIOUR OF THE SPIN TRANSITION COMPOUNDS DURING PHOTO-EXCITATION AND RELAXATION, Journal of Optoelectronics and Advanced Materials Vol. 5, Iss. 1, pp. 261-266 (2003)