Abstract
Contrary to previous studies that identified the ground state crystal structure of the entire R3Co series (R is a rare earth) as orthorhombic Pnma, we show that Y3Co undergoes a structural phase transition at Ttâ‰160 K. Single crystal neutron diffraction data reveal that at Tt the trigonal prisms formed by a cobalt atom and its six nearest-neighbor yttrium atoms experience distortions accompanied by notable changes of the Y-Co distances. The formation of the low-temperature phase is accompanied by a pronounced lattice distortion and anomalies seen in heat capacity and resistivity measurements. Density functional theory calculations reveal a dynamical instability of the Pnma structure of Y3Co. In particular, a transversal acoustic phonon mode along the (00ξ) direction has imaginary frequencies at ξ<1/4. Employing inelastic neutron scattering measurements we find a strong damping of the (00ξ) phonon mode below a critical temperature Tt. The observed structural transformation causes the reduction of dimensionality of electronic bands and decreases the electronic density of states at the Fermi level that identifies Y3Co as a system with the charge density wave instability.
Original language | English |
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Article number | 024117 |
Journal | Physical Review B - Condensed Matter and Materials Physics |
Volume | 88 |
Issue number | 2 |
DOIs | |
State | Published - Jul 26 2013 |