Metal Substitution Effects on the Charge Transport and Spin Crossover Properties of Fe1–xZnx(Htrz)2(trz)(BF4) (trz = Triazole)

摘要

In this study we analyze the metal substitution effects on the structural, morphological, charge transport, and spin transition properties of the [Fe1–xZnx(Htrz)2(trz)](BF4) (trz = triazole, x = 0, 0.26, or 0.43) compound using electron microscopy, powder X-ray diffraction, optical reflectivity, Raman, FTIR, 57Fe Mössbauer, and broadband (10–2–106 Hz) dielectric spectroscopies. The crystal structure and the morphology of the objects remain nearly unaffected, whereas the thermal spin transition shifts from 362 to 316 K and the thermal hysteresis width decreases from 45 to 8 K for increasing values of x. For each compound the electrical conductivity drops when the iron(II) electronic configuration is switched from the low-spin to the high-spin state. A strong overall decrease in conductivity with increasing Zn concentration is also observed in both spin states. These results, together with the analysis of the charge carrier dynamics, suggest that the ferrous ions participate directly in the charge transport mechanism, explaining the strong spin-state dependence of the electrical properties in this compound.