Neutron scattering study of magnetic excitations in YBa sub 2 Cu sub 3 O sub 6+ x

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Physical Review (Section) B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.40.4503· OSTI ID:5525035

Tranquada, J M; Shirane, G ^[1]; Keimer, B ^[2]; Shamoto, S; Sato, M ^[3]

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1. Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (US)
2. Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
3. Institute for Molecular Science, Okazaki 444, Japan

Inelastic neutron scattering has been used to study magnetic excitations in several single crystals of YBa{sub 2}Cu{sub 3}O{sub 6+{ital x}}. In particular, an extensive study of spin waves in a large crystal with {ital x}=0.3 has been performed. As in La{sub 2}CuO{sub 4}, a very large superexchange is found within the CuO{sub 2} layers, with {ital J}{sub {parallel}}=80{sub {minus}30}{sup +60} meV. The optical-mode spin-wave energies are higher than 30 meV, indicating that {ital J}{sub {perpendicular}1}, the coupling between nearest-neighbor CuO{sub 2} planes, is {approx gt}2 meV. From the dispersion and splitting of the acoustic modes, we obtain values of 0.020{plus minus}0.005 meV for the effective exchange between next-nearest-neighbor layers, {ital J}{sub {perpendicular}2}, and 0.035{plus minus}0.005 meV for the anisotropy parameter {ital D}. The weak anisotropy gives the planes an {ital XY}-like symmetry; no evidence has been found for any in-plane anisotropy. The CuO{sub 2} bilayers remain strongly correlated well above {ital T}{sub {ital N}}, and dispersion of the acoustic modes appears 30 K above {ital T}{sub {ital N}}. The decrease of the magnetic order parameter below 30 K in the {ital x}=0.3 crystal is interpreted as the onset of an incoherent ordering of Cu moments in the oxygen-deficient CuO{sub {ital x}} layers. Low-energy inelastic scattering associated with the transition is also observed. Searches for low-energy magnetic fluctuations in several superconducting single crystals have so far been unsuccessful.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5525035
• Journal Information: Physical Review (Section) B: Condensed Matter; (USA), Vol. 40:7; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
SPIN WAVES
COPPER OXIDES
YTTRIUM OXIDES
INELASTIC SCATTERING
LAYERS
MAGNETIC PROPERTIES
MONOCRYSTALS
NEUTRON DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
CRYSTALS
DIFFRACTION
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties