Hyperfine fields at the Ba site in the antiferromagnet YBa{sub 2}Cu{sub 3}O{sub 6.05}

Journal Article · Sat Jun 01 00:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.14268· OSTI ID:284384

Lombardi, A; Mali, M; Roos, J; Brinkmann, D ^[1]

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1. Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland)

We report a Ba nuclear quadrupole resonance (NQR) study of the antiferromagnetic state of YBa{sub 2}Cu{sub 3}O{sub 6.05} (N{acute e}el temperature {ital T}{sub {ital N}} = 415 K) performed between 16 and 402 K. The Zeeman perturbed {sup 137}Ba NQR spectrum yields information on two hyperfine fields present at the Ba site: the electric field gradient (EFG) and the internal magnetic field arising from the Cu(2) sublattice magnetization. The absolute value of the EFG is in remarkable agreement with cluster and band structure calculations thus demonstrating again that both methods provide a satisfying electronic bond picture for the Y-Ba-Cu-O compounds [except for the planar Cu(2) site]. The temperature dependence of the EFG arises from thermal expansion only. The internal field, {ital B}({ital T}), has been deduced from the modulation of the Ba spin-echo intensity. A calculation of the dipolar field at the Ba site produced by Cu(2) {ital d} electrons yields a value that is about three times larger than the experimental result. The discrepancy could be explained by assuming that part of the magnetic moment is located at oxygen ions. The temperature variation of {ital B}({ital T}) follows, up to 402 K, a power law [{ital B}(0){minus}{ital B}({ital T})]/{ital B}(0)={ital AT}{sup {alpha}} with {alpha} = 1.82(22) which agrees quite well with the result of a Cu(2) in-plane determination of the sublattice magnetization. Furthermore, this result is in accord with a spin-wave model for a quasi-two-dimensional (2D) antiferromagnet. The {open_quote}{open_quote}critical exponent{close_quote}{close_quote} {beta} is estimated to be {le} 0.18 which is in accord with values proposed by models for 2D ordered magnetic systems. Thus YBa{sub 2}Cu{sub 3}O{sub 6.05} behaves, in terms of its spin dynamics, as a quasi-2D antiferromagnet and this character can be studied either at out-of-plane Ba or at in-plane Cu(2) sites. {copyright} {ital 1996 The American Physical Society.}

• OSTI ID: 284384
• Journal Information: Physical Review, B: Condensed Matter, Vol. 53, Issue 21; Other Information: PBD: Jun 1996
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
HIGH-TC SUPERCONDUCTORS
HYPERFINE STRUCTURE
ANTIFERROMAGNETIC MATERIALS
COPPER OXIDES
BARIUM OXIDES
YTTRIUM OXIDES
NUCLEAR QUADRUPOLE RESONANCE
NEEL TEMPERATURE
ELECTRIC FIELDS
MAGNETIC FIELDS
MAGNETIZATION
THERMAL EXPANSION
SPIN ECHO
TEMPERATURE DEPENDENCE
SPIN WAVES
ELECTRIC FIELD GRADIENTS
CRITICAL EXPONENTS