Negative volume thermal expansion via orbital and magnetic orders in Ca2Ru1-xCrxO4(0<x<0.13)

T. F. Qi, O. B. Korneta, S. Parkin, L. E. De Long, P. Schlottmann, G. Cao

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Ca2RuO4 undergoes a metal-insulator transition at TMI=357K, followed by a well-separated transition to antiferromagnetic order at TN=110K. Dilute Cr doping for Ru reduces the temperature of the orthorhombic distortion at TMI and induces ferromagnetic behavior at TC. The lattice volume V of Ca 2Ru1-xCrxO4 (0<x<0.13) abruptly expands with cooling at both TMI and TC, giving rise to a total volume expansion ΔV/V≈1%, which sharply contrasts the smooth temperature dependence of the few known examples of negative volume thermal expansion driven by anharmonic phonon modes. In addition, the near absence of volume thermal expansion between TC and TMI represents an Invar effect. The two phase transitions, which surprisingly mimic the classic freezing transition of water, suggest an exotic ground state driven by an extraordinary coupling between spin, orbit, and lattice degrees of freedom.

Original languageEnglish
Article number177203
JournalPhysical Review Letters
Issue number17
StatePublished - Oct 22 2010

ASJC Scopus subject areas

  • General Physics and Astronomy


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