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Journal of Thermal Analysis and Calorimetry

, Volume 113, Issue 3, pp 1197–1201 | Cite as

Magnetic transition in dimerized radical cation salt of (BPDT-TTF)2ICl2 studied by heat capacity measurements

  • Guoyang Guan
  • Shuhei Fukuoka
  • Satoshi Yamashita
  • Takashi Yamamoto
  • Hiromi Taniguchi
  • Yasuhiro NakazawaEmail author
Article

Abstract

Thermodynamic investigation using the relaxation calorimetry technique and the microchip calorimetry technique is performed to clarify low-temperature behaviors of a radical cation salt consisting of a donor molecule of bispropylenedithiotetrathiafulvalene (BPDT-TTF) and a linear anion of \({{\text{ICl}}_{2}^{-}}\). This compound has a layered structure similar to numerous BEDT-TTF compounds. The donor molecules form a dimerized arrangement in the layer. Temperature dependence of heat capacity obtained by the relaxation technique shows a broad hump structure around 20–25 K corresponding to the temperature where the magnetic susceptibility shows a drastic decrease due to the formation of the singlet spin state. The microchip calorimetry technique detected a step-like anomaly around 23 K in the temperature dependence of C p T −1 of which entropy is evaluated as only few % of Rln2 corresponding to the full entropy of localized π-electrons located on each dimer unit. The negligibly small T-linear term in the low-temperature heat capacity and absence of magnetic fields dependence below 3.2 K predict opening of rigid gap structure in the spin excitations, which is consistent with a spin-singlet formation due to the formation of spin-Peierls type ordering or charge ordering state.

Keywords

Heat capacity Organic donor molecules Spin–Peierls transition Dimer–Mott system 

Notes

Acknowledgments

This work was supported in part by Grant-in-Aid for Scientific Research (Nos. 23110717 and 22340098) from the MEXT and JSPS.

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2013

Authors and Affiliations

  • Guoyang Guan
    • 1
  • Shuhei Fukuoka
    • 1
  • Satoshi Yamashita
    • 1
  • Takashi Yamamoto
    • 1
  • Hiromi Taniguchi
    • 2
  • Yasuhiro Nakazawa
    • 1
    Email author
  1. 1.Department of Chemistry, Graduate School of ScienceOsaka UniversityOsakaJapan
  2. 2.Department of Physics, Graduate School of ScienceSaitama UniversitySaitamaJapan

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