Lattice instability and low-temperature phase transition in Pr sub 2 NiO sub 4

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.13766· OSTI ID:5691016

Martriaanez, J L; Fernandez-Driaaaz, M T; Rodrriaaguez-Carvajal, J ^[1]; Odier, P ^[2]

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1. Institute Laue-Langevin, Boite Postale 156-X, F-38042, Grenoble CEDEX, France (FR)
2. Centre de Recherches sur la Physique des Hautes Temperatures, CNRS, F-45071 Orleans, France (FR)

Some layered perovskites with general formulas {ital R}{sub 2}{ital M}O{sub 4} ({ital R}=rare earth; {ital M}=Cu, Ni or Co) undergo a sequence of structural phase transitions. The high-temperature tetragonal phase (HTT) is transformed to the low-temperature orthorhombic phase (LTO) at {ital T}{sub {ital c}2}, after further cooling, there is a new low-temperature tetragonal (LTT) phase at {ital T}{sub {ital c}1}. The soft mode behavior at {ital T}{sub {ital c}1} is observed with inelastic neutron scattering in this family of compounds for Pr{sub 2}NiO{sub 4}. One of the two branches, of the doubly degenerate {ital X}-point phonon of the HTT phase, becomes softer at {ital T}{sub {ital c}1}. In the LTT phase, this phonon branch is stiffer and appears at higher energy. The orthorhombic strain and the soft-mode frequency undergo a discontinuous jump at the transition temperature, indicating a clear first-order character of this phase transformation. From these data, the dynamics of the LTO{r arrow}LTT phase transformation in the insulator Pr{sub 2}NiO{sub 4+{delta}} ({delta}=0) can be well characterized. For La{sub 2{minus}{ital x}}Ba{sub {ital x}}CuO{sub 4} ({ital x}=1/8) the same kind of transition is observed, which coincides with the suppression of the superconducting state, but the presence of free charge carriers may complicate the interpretation of the results in this case.

• OSTI ID: 5691016
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:16; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRITICAL TEMPERATURE
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DIFFRACTION
HIGH-TC SUPERCONDUCTORS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
NEUTRON DIFFRACTION
NICKEL COMPOUNDS
NICKEL OXIDES
OXIDES
OXYGEN COMPOUNDS
PEROVSKITES
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SCATTERING
SUPERCONDUCTORS
TETRAGONAL LATTICES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE