Dielectric slowing down toward the magnetically ordered state in a polar conductor (EDT-TTFVO)2FeBr4

Eiichi Negishi, Shun Yabuta, Naoki Toyota, Takuya Matsumoto, Toyonari Sugimoto

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We have measured the dielectric response as a function of both frequency (f = 0.3 Hz-100 kHz) and electric bias field for a quasi-one-dimensional, polar conductor (EDT-TTFVO)2FeBr4 undergoing a ferrimagnetic-like transition at TC ∼ 0:9 K. Around T* = 15 K, the dielectric constant at low f exhibits a peak that shifts to higher T at higher f , being reminiscent of relaxor ferroelectrics with glassy polarizations. Since this dielectric anomaly is also present in the nonmagnetic isostructural GaBr4 salt, the polarizations may be ascribed to both π and σ electrons localized on the polar donor. At TC < T < 7 K, the complex dielectric constant clearly exhibits a Debye relaxation, and the relaxation time follows a critical behavior as (T - T0) -nτ (nτ = 6.5) toward T0 = 0.75 ± 0.15K just very close to TC. This phenomenon of the dielectric-slowing-down toward the magnetically ordered state is discussed as a novel type of multifunctional coupling in the short-range ordered state between the possible electric polarization in the distorted tetrahedral anion and the centered d spin of 5/2, the latter of which, eventually at TC, may induce the magnetic order with π spins of 1/2 disproportionately localized on the polar donors.

Original languageEnglish
Article number093703
JournalJournal of the Physical Society of Japan
Volume76
Issue number9
DOIs
Publication statusPublished - 2007 Sep 1

Keywords

  • (EDT-TTFVO)FeBr
  • Charge disproportionation
  • Debye relaxation
  • Dielectric slowing down
  • Ferrimagnetic state
  • Order-disorder transition
  • Polar conductor
  • Relaxor ferroelectric

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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