Optical study of Pr1-xCaxMnO3(x = 0.4) in a magnetic field: Variation of electronic structure with charge ordering and disordering phase transitions

Y. Okimoto, Y. Tomioka, Y. Onose, Y. Otsuka, Y. Tokura

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90 Citations (Scopus)

Abstract

The temperature (10-290 K) and magnetic-field (0-7 T) dependencies of optical spectra and their anisotropy have been investigated for a single crystal of Pr1-xCaxMnO3(x = 0.4), which undergoes a charge and orbital ordering transition at Tco = 235 K. A clear anisotropic feature has been observed between the b- and c-axis polarized optical conductivity spectra [σ(ω)] at 10 K, reflecting a pattern of spatial charge and orbital ordering. The gap value of the charge-ordered (CO) state is estimated to be ≈ 0.18eV in the ground state. σ(ω) is drastically transformed from an anisotropic gaplike shape into an isotropic metallic band with a conspicuous spectral weight transfer over a wide photon energy region (0.05-3 eV) by application of a magnetic field of 7 T. As the magnetic field is decreased from 7 T, such metallic σ(ω) suddenly becomes gaplike again around 4.5 T, yet the anisotropy between both polarizations is decreased perhaps owing to orbital disordering. The temperature dependence of the b-axis polarized σ(ω) was investigated in a constant magnetic field of 7 T. As the temperature decreases, the onset energy of σ(ω) shows a blueshift from Tco down to the antiferromagnetic spin ordering temperature TN, but shows a redshift once the spin ordering takes place below TN. This result indicates that the charge gap value as the order parameter of the CO state couples with the spin ordering.

Original languageEnglish
Pages (from-to)7401-7408
Number of pages8
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume59
Issue number11
DOIs
Publication statusPublished - 1999 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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