Significant softening of c66 and hidden order parameter in the magnetic ordered state of La2-xCaxCoO4 (0.4≤x≤0.7)

Kazumasa Horigane, T. Kobayashi, M. Suzuki, K. Abe, K. Asai, Jun Akimitsu

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We have measured the longitudinal and transverse sound velocities of La2-xCaxCoO4 (0.4≤x≤0.7) propagating along [100], [110], and [001] from 200 K down to 3 K with a frequency of 10 MHz. It was found that c66 shows a remarkable softening below Co 2+ spin-ordering temperature TN in the whole doping range, while c11-c12/2 exhibits a clear hardening below Co 3+ spin-ordering temperature TN2 only when x=0.5. To explain the observed anomaly, the Landau free energy for the La 2-xCaxCoO4 system has been constructed, including the coupling energy between elastic strains and a two-dimensional order parameter (Q1, Q2), having a spatial modulation along [110] or [1̄ 10]. We argued that this represents orbital order, and it is this order that leads to the softening of c66.

Original languageEnglish
Article number144108
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number14
DOIs
Publication statusPublished - Oct 27 2008
Externally publishedYes

Fingerprint

spin temperature
softening
Acoustic wave velocity
acoustic velocity
hardening
Free energy
Hardening
free energy
Doping (additives)
Modulation
anomalies
modulation
orbitals
Temperature
energy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Significant softening of c66 and hidden order parameter in the magnetic ordered state of La2-xCaxCoO4 (0.4≤x≤0.7). / Horigane, Kazumasa; Kobayashi, T.; Suzuki, M.; Abe, K.; Asai, K.; Akimitsu, Jun.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 78, No. 14, 144108, 27.10.2008.

Research output: Contribution to journalArticle

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AU - Abe, K.

AU - Asai, K.

AU - Akimitsu, Jun

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