Dielectric characterization of [ Fe ( NH 2 − trz ) 3 ] Br 2 H 2 O thermal spin crossover compound by terahertz time domain spectroscopy

• Published in: Applied physics letters Vol. 87; no. 24; pp. 244103 - 244103-3
• Main Authors: Mounaix, P., Lascoux, N., Degert, J., Freysz, E., Kobayashi, A., Daro, N., Létard, J.-F.
• Format: Journal Article
• Published: American Institute of Physics 08-12-2005
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.2143123

The complex optical index refraction of an iron (II) spin-crossover coordination polymer is measured in the Terahertz frequency range by Terahertz time-domain spectroscopy (THz-TDS). By scanning the temperature from 288 to 333 K, we have recorded the evolution of the THz spectrum within the low spin - high spin thermal hysteresis loop. We were able to simultaneously infer the refractive index and absorption variations. The low spin-high spin transition has a marked spectral signature in the millimeter wavelength. In the 0.1-0.6 THz frequency range, the variation of real and imaginary part of the index of refraction is 6% and 20%, respectively. A marked absorption is observed above 500 GHz. The THz-TDS provides a clear direct fingerprint of this class of materials, which are interestingly potential candidates for optical data storage and processing devices.