Metallic “Ferroelectricity” in the Pyrochlore [Formula presented]

I. A. Sergienko, V. Keppens, M. McGuire, R. Jin, J. He, S. H. Curnoe, B. C. Sales, P. Blaha, D. J. Singh, K. Schwarz, D. Mandrus

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Abstract

A class of materials known as “ferroelectric metals” was discussed theoretically by Anderson and Blount in 1965 [Phys. Rev. Lett. 14, 217 (1965) 10.1103/PhysRevLett.14.217], but to date no examples of this class of materials have been reported. Here we present measurements of the elastic moduli of [Formula presented] through the 200 K cubic-to-tetragonal phase transition. A Landau analysis of the moduli reveals that the transition is consistent with [Formula presented] being classified as a ferroelectric metal in the weaker sense described by Anderson and Blount (loss of a center of symmetry). First-principles calculations of the lattice instabilities indicate that the dominant lattice instability corresponds to a twofold degenerate mode with [Formula presented] symmetry and that motions of the O ions forming the O octahedra dominate the energetics of the transition.

Original languageEnglish
JournalPhysical Review Letters
Volume92
Issue number6
DOIs
StatePublished - 2004
Externally publishedYes

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