Electronic phase transition of the valence-fluctuating fulleride Eu 2.75C60

Yusuke Yamanari, Yuta Suzuki, Kumiko Imai, Eiji Shikoh, Akihiko Fujiwara, Naoko Kawasaki, Naoshi Ikeda, Yoshihiro Kubozono, Takashi Kambe

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Abstract

The electronic properties of Eu2.75C60 are studied using magnetic susceptibility and electron spin resonance (ESR) from 2 to 300 K. Both the magnetic susceptibility and the ESR parameters clearly show an anomaly around the valence transition temperature, TV = 70 K. The magnetic susceptibility shows weak temperature dependence above TV, while it changes drastically to Curie-Weiss behavior below TV. The low-temperature susceptibility can be reproduced by assuming the moment of free Eu2+ ions. This result reveals that Eu2.75C60 changes from the intermediate valence state to the divalent state below T V. Although ESR signals above TV should be attributed to conduction electrons, the ESR intensity below TV follows the Curie-Weiss law with a distinct increase in the g-factor. This should be associated with a strong localization of π electrons. We also found that, below ∼17 K, the isothermal magnetization exhibits a weak hysteresis and thermoremanent magnetization appears. These results suggest that valence-ordered Eu2.75C60 undergoes antiferromagnetic ordering with a weak ferromagnetic component at the Néel temperature, TN = 17 K.

Original languageEnglish
Article number245103
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume83
Issue number24
DOIs
Publication statusPublished - Jun 3 2011

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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