Broad-Band Dielectric Spectroscopy Reveals Peak Values of Conductivity and Permittivity Switching upon Spin Crossover

Ion Soroceanu (1) , Adrian Graur (1) , Eugen Coca (1) , Lionel Salmon (2) , Gábor Molnár (2) , Philippe Demont (3) , Azzedine Bousseksou (2) , Aurelian Rotaru (1)

1 USU - University Stefan cel Mare of Suceava
2 LCC - Laboratoire de chimie de coordination
3 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

We use broad-band dielectric spectroscopy to investigate the spin-state dependence of electrical properties of the [Fe(Htrz)2(trz)](BF4) spin crossover complex. We show that the Havriliak–Negami theory can fully describe the variation of the complex dielectric permittivity of the material across the pressure–temperature phase diagram. The analysis reveals three dielectric relaxation processes, which we attribute to electrode/interface polarization, dipole relaxation, and charge transport relaxation. The contribution of the latter appears significant to the dielectric strength. Remarkably, the permittivity and conductivity changes between the high spin and low spin states are amplified at the corresponding relaxation frequencies.

Mots clés: Broad-band dielectric spectroscopy; Spin Crossover

Domaines: Matériaux; Matériaux

Ion Soroceanu, Adrian Graur, Eugen Coca, Lionel Salmon, Gábor Molnár, et al.. Broad-Band Dielectric Spectroscopy Reveals Peak Values of Conductivity and Permittivity Switching upon Spin Crossover. Journal of Physical Chemistry Letters, 2019, pp.7391-7396. ⟨10.1021/acs.jpclett.9b02678⟩. ⟨hal-02378686⟩