Photoinduced Phase Transition and Relaxation Behavior in a Spin-Crossover Fe (II) Complex Nafion-[Fe(Htrz)₃] Film

Abstract

We have observed a photoinduced phase transition (PIPT) in a spin-crossover Fe (II) complex Nafion-[Fe(Htrz)₃] film (Nafion is an ion exchange polymer film, and Htrz=1, 2, 4-1H-triazole) from a low-spin (LS) state (S=0) to a high-spin (HS) state (S=2) below 150 K. The phototransferred HS state relaxes to the initial LS state, exhibiting a nonexponential time behavior, which has been interpreted in terms of the critical nucleation and subsequent growth of the LS clusters. We have also observed that the decay time τ_c is approximately temperature-independent in the low temperature range of 4.2-20 K, and then decreases exponentially with temperature.