Spin-entropy driven charge-transfer phase transition in iron mixed-valence system

N. Kojima*, M. Itoi, Y. Ono, M. Okubo, M. Enomoto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We have synthesized iron mixed-valence complexes, (n-CnH2n+1)4N[FeIIFe IIIX3] (X = mto (C2O3S), dto (C2O2S2), tto (C2OS3)) and have investigated their physical properties by means of 57Fe Mössbauer spectroscopy, magnetic susceptibility and electrical resistivity measurements. From the analysis of 57Fe Mössbauer spectra, magnetic susceptibility and electrical resistivity, we have discovered a new type of first order phase transition around 120 K for (n-CnH2n+1)4N[FeIIFe III(dto)3](n = 3, 4), where the charge-transfer transition between FeII and FeIII occurs reversibly. In the higher temperature phase, the FeIII (S = 1/2) and FeII (S = 2) sites are co-ordinated by six S atoms and six O atoms, respectively. In the lower temperature phase, on the other hand, the FeIII (S = 5/2) and FeII (S = 0) sites are co-ordinated by six O atoms and six S atoms, respectively. Moreover, we have found a ferromagnetic phase transition in this system. The ferromagnetic order is induced by the charge-transfer interaction between the FeIII and FeII sites. We propose various multifunctional properties for (nCnH2n+1)4N[FeIIFe III(mto)3] and (n-CnH2n+1)4N[FeIIFe III(tto)3].

Original languageEnglish
Pages (from-to)181-189
Number of pages9
JournalMaterials Science- Poland
Issue number2
Publication statusPublished - 2003
Externally publishedYes


  • Charge-transfer
  • Ferromagnetism
  • Mixed valence
  • Phase transition
  • Spin crossover

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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