16. Real-Time Observation of Spin-Transitions by Optical Microscopy

  1. François Varret1,
  2. Christian Chong1,
  3. Ahmed Slimani1,
  4. Damien Garrot1,
  5. Yann Garcia2 and
  6. Anil D. Naik2

Published Online: 18 JAN 2013

DOI: 10.1002/9781118519301.ch16

Spin-Crossover Materials: Properties and Applications

Spin-Crossover Materials: Properties and Applications

How to Cite

Varret, F., Chong, C., Slimani, A., Garrot, D., Garcia, Y. and Naik, A. D. (2013) Real-Time Observation of Spin-Transitions by Optical Microscopy, in Spin-Crossover Materials: Properties and Applications (ed M. A. HALCROW), John Wiley & Sons Ltd, Oxford, UK. doi: 10.1002/9781118519301.ch16

Editor Information

  1. School of Chemistry, University of Leeds, UK

Author Information

  1. 1

    GEMAC Université de Versailles, France

  2. 2

    Institute of Condensed Matter and Nanosciences, MOST – Inorganic Chemistry Université Catholique de Louvain, Belgium

Publication History

  1. Published Online: 18 JAN 2013
  2. Published Print: 15 FEB 2013

ISBN Information

Print ISBN: 9781119998679

Online ISBN: 9781118519301



  • colorimetric investigation;
  • cross-polarizer geometry;
  • nucleation;
  • optical microscopy (OM);
  • organic crystals;
  • spin-transition crystals


This chapter discusses real-time observation of spin-transitions by optical microscopy (OM). The physical features revealed by OM of spin-transition crystals are consistent with well-established observations on (first-order) phase transitions in organic crystals. That is, they evidence a nucleation and growth process for the spin transition. The authors, therefore, reached the crucial conclusion that the spin-transition obeys a multiscale, stress-driven, nucleation and growth process. In the present case of switchable molecular solids, due to their thermo- and photochromic properties, OM can be used as a local colorimetric tool. The change in optical density (OD) associated with a specific absorption band enables local measurements of the HS fraction of the system. The use of cross-polarizer geometry may reveal the onset of a symmetry change concomitant to the spin change, thus allowing an investigation of the interplay between the spin and structural changes. Cross-polarizer geometry may also reveal the presence of internal stresses.