Raman study of [ital T][prime]-phase distortion in [ital R][sub 2]CuO[sub 4] compounds ([ital R]=Nd,Sm,Eu,Gd)

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.48.7565· OSTI ID:6050475

Laguna, M A

We present a Raman study of the appearance of structural distortions in [ital T][prime]-phase cuprates [ital R][sub 2[minus][ital x]]Ce[sub [ital x]]CuO[sub 4] ([ital R]=Sm,Eu,Gd) upon [ital R] atomic number increase. Besides some anomalies in the frequencies of the allowed modes, the distortion from the [ital T][prime] phase is evidenced in Gd[sub 2]CuO[sub 4] by the appearance of an additional mode with [ital B][sub 1[ital g]] symmetry, [ital B][sub 1[ital g]][sup *], that we assign to the motion of the in-plane oxygen atoms, O(1). This mode, which appears incipiently in Eu[sub 2]CuO[sub 4] and SmGdCuO[sub 4], is formally forbidden by symmetry, and would be activated by O(1) displacement resulting in a distorted CuO[sub 2] plane. This interpretation is in agreement with previous experimental results either of structural or magnetic type. The appearance of weak ferromagnetism for [ital R]=Gd and beyond, for instance, is incompatible with perfect [ital T][prime]-phase structure. We compare the results in pure compounds with those that are Ce doped and show that the [ital B][sub 1[ital g]][sup *] activity decreases with respect to that of the [ital B][sub 1[ital g]] mode as increasing amounts of Ce are introduced in the lattice; this is interpreted as a consequence of [ital T][prime]-phase stabilization upon doping. Temperature-dependence spectra are also presented and discussed.

• OSTI ID: 6050475
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 48:10; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
EUROPIUM COMPOUNDS
EUROPIUM OXIDES
GADOLINIUM COMPOUNDS
GADOLINIUM OXIDES
MAGNETIC PROPERTIES
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
RAMAN SPECTRA
RARE EARTH COMPOUNDS
SAMARIUM COMPOUNDS
SAMARIUM OXIDES
SPECTRA
STRAINS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS