Pressure effect on charge-transfer phase transition in a mixed-valence iron complex, (n-C3H7)4N[FeIIFeIII(dto)3] (dto = C2O2S2)

• Published in: Journal of the Physical Society of Japan 2002-12, Vol.71 (12), p.3016-3020
• Main Authors: KOBAYASHI, Yoshihiko, ITOI, Miho, KOJIMA, Norimichi, ASAI, Kichizo
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Magnetic properties and materials; Magnetization curves, hysteresis, Barkhausen and related effects; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Physics
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/jpsj.71.3016

We have investigated the hydrostatic pressure effect on the charge-transfer phase transition between FeII and FeIII in a mixed-valence iron complex, (n-C3H7)4N[FeIIFeIII(dto)3] (dto = C2O2S2) up to 0.9 GPa. The transition temperature of the charge-transfer phase transition increases almost linearly with increasing applied hydrostatic pressure (∼100 K/GPa), while the ferromagnetic Curie temperature (Tc ∼ 7 K) changes only slightly. The results suggest that the applied hydrostatic pressure stabilizes the low-temperature phase [FeII(S=0)-FeIII(S=5/2)] through the compression of the lattice volume. A phenomenological model taking into account the elastic interactions as a molecular-field explains the characteristics of the charge-transfer phase transition. The analysis of the results of the model calculation suggests that the lattice volume of the high-temperature phase is only about 0.2% larger than that of the low-temperature phase, and a lattice deformation of [FeIIFeIII(dto)3] molecules without the lattice expansion plays an important role in the first-order character of the charge-transfer phase transition.