Time-domain terahertz spectroscopy of spin state transition in [Fe(NH2 − trz)3]2+ spin crossover compounds

Abstract

We have measured the evolution of the THz spectrum of iron(II) spin crossover compounds within the low-spin/high-spin thermal hysteresis loop in the 0.6–6 THz frequency range. This study enabled to follow both the variations of the refractive optical index and absorption during the spin state transition. Marked absorptions centered ∼2 – 3 THz and ∼5 THz shifting with the spin state are revealed. Our work provides a means to store optically information and to read it out in the THz domain and also offers indications about the structural evolution occurring during the spin state transition.

Spin-Crossover Materials towards Microwave Radiation Switches

“…The values of absorption factor are relatively low compared with those found for triazole complexes in other spectral regions, including THz region39, where an absorption coefficient is estimated at 400–600 cm −1 . This is probably because the investigated frequencies do not correspond to the characteristic frequencies of absorption in 1 and the interaction with microwaves is determined by dielectric losses solely.…”

Impact of Spin State Transition on Vibrations of [Fe–(PM–BiA)2(NCS)2] and [Fe–(PM–PEA)2(NCS)2] Spin Crossover Compounds: Experimental and Theoretical Far IR and Raman Study

“…The latter have broader absorption peaks (Δν ≈ 1 THz) in the THz spectral range. [26] As expected, and thanks to the good crystal- line structure of SCO microcrystals, the absorption peaks are narrower (Δν ≈ 1 THz). It is interesting to note that the IR absorption peaks of both compounds present marked differences both in position and amplitude.…”

“…This makes it possible to retrieve the absorption spectrum of the sample in the LS and HS states. [32,33] The THz spectra were collected in the LS state at T = 100 K and at T = 293 K in the HS state.…”

Second‐Harmonic and Terahertz Generation in a Prussian‐Blue Analogue

“…[21] In short, a THz beam, consisting of a single-cycle THz wave, was emitted into air ionized by the fundamental and the second-harmonic waves of 50 fs pulses centered at λ = 800 nm. After transmission through the sample, the wave was measured by electro-optical (EO) sampling in a 200 μm thick <110> GaP crystal.…”

“…It also made it possible to retrieve the absorption spectrum of the sample. [21,22] For the THz generation experiment, a 300 μm thick pellet was excited by 160 fs pulses centered at λ = 1.1 μm, provided by the OPA. The THz wave was generated without focusing the excitation pulses.…”