Spatiotemporal dynamics of the spin transition in [Fe(HB(tz)3)2] single crystals

Karl Ridier, Sylvain Rat, Helena J. Shepherd, Lionel Salmon, William Nicolazzi, Gábor Molnár, and Azzedine Bousseksou
Phys. Rev. B 96, 134106 – Published 11 October 2017
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Abstract

The spatiotemporal dynamics of the spin transition have been thoroughly investigated in single crystals of the mononuclear spin-crossover (SCO) complex [Fe(HB(tz)3)2] (tz=1,2,4-triazol-1-yl) by optical microscopy. This compound exhibits an abrupt spin transition centered at 334 K with a narrow thermal hysteresis loop of 1 K (first-order transition). Most single crystals of this compound reveal exceptional resilience upon repeated switching (several hundred cycles), which allowed repeatable and quantitative measurements of the spatiotemporal dynamics of the nucleation and growth processes to be carried out. These experiments revealed remarkable properties of the thermally induced spin transition: high stability of the thermal hysteresis loop, unprecedented large velocities of the macroscopic low-spin/high-spin phase boundaries up to 500 µm/s, and no visible dependency on the temperature scan rate. We have also studied the dynamics of the low-spin → high-spin transition induced by a local photothermal excitation generated by a spatially localized (Ø=2μm) continuous laser beam. Interesting phenomena have been evidenced both in quasistatic and dynamic conditions (e.g., threshold effects and long incubation periods, thermal activation of the phase boundary propagation, stabilization of the crystal in a stationary biphasic state, and thermal cutoff frequency). These measurements demonstrated the importance of thermal effects in the transition dynamics, and they enabled an accurate determination of the thermal properties of the SCO compound in the framework of a simple theoretical model.

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  • Received 1 August 2017

DOI:https://doi.org/10.1103/PhysRevB.96.134106

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Karl Ridier1, Sylvain Rat1, Helena J. Shepherd2, Lionel Salmon1, William Nicolazzi1, Gábor Molnár1,*, and Azzedine Bousseksou1,†

  • 1Laboratoire de Chimie de Coordination, CNRS UPR-8241, 205 route de Narbonne, F-31077 Toulouse, France
  • 2School of Physical Sciences, University of Kent, Park Wood Road, Canterbury CT2 7NH, United Kingdom

  • *gabor.molnar@lcc-toulouse.fr,
  • azzedine.bousseksou@lcc-toulouse.fr

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Issue

Vol. 96, Iss. 13 — 1 October 2017

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