Significance of Al doping for antiferromagnetic AFII ordering in YBa{sub 2}Cu{sub 3{minus}{ital x}}Al{sub {ital x}}O{sub 6+{delta}} materials: A single-crystal neutron-diffraction study

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.52.9601· OSTI ID:249433

Brecht, E; Schmahl, W W; Fuess, H ^[1]; Casalta, H; Schleger, P; Lebech, B; Andersen, N H ^[2]; Wolf, T ^[3]

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1. Fachbereich Materialwissenschaft-Strukturforschung, Technische Hochschule Darmstadt, Petersenstrasse 20, D-64287 Darmstadt (Germany)
2. Riso National Laboratory, Department of Solid State Physics, DK-4000 Roskilde (Denmark)
3. Forschungszentrum Karlsruhe, Institut fuer Technische Physik, P.O. Box 3640, D-76021 Karlsruhe (Germany)

Aluminum-doped, oxygen-deficient YBa{sub 2}Cu{sub 3{minus}{ital x}}Al{sub {ital x}}O{sub 6+{delta}} single crystals with different Al contents {ital x} (0{le}{ital x}{le}0.19) and O contents (0.18{le}{delta}{le}0.36) were studied by magnetic neutron diffraction. All of the Al-doped single crystals show two magnetic transitions, the first between the paramagnetic state and the AFI phase, and a second transition at low temperatures between the AFI and the AFII phase. The Neel temperature {ital T}{sub {ital N}} of the antiferromagnetic AFI phase is found to be insensitive to the Al content {ital x} as well as the O content 6+{delta} in the {ital x}-{delta} region investigated so far. In a limited temperature interval the order parameter shows the components of both the AFI and AFII phases indicating competing interactions. For some crystals a complete reordering to the AFII phase at 4.2 K can be observed. Although the antiferromagnetic ordering pattern is different for the AFI and AFII phase, the ordered moments on the Cu sites are within the experimental error ({l_angle}{ital S}{r_angle}{sub Cu(2)}{approx}0.56{mu}{sub {ital B}}, {l_angle}{ital S}{r_angle}{sub Cu(1)}{approx}0{mu}{sub {ital B}}) identical in the two phases. Comparison of Al-doped crystals with pure crystals of the same oxygen content shows that the presence of excess oxygen only ({delta}{gt}0) is not sufficient to obtain the AFII ordering at low temperatures. Instead, the AFII ordering is triggered by the creation of the local magnetic moments in Cu-O-Al chain fragments.

• OSTI ID: 249433
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 13 Vol. 52; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ALUMINIUM
ANTIFERROMAGNETISM
BARIUM OXIDES
COPPER OXIDES
HIGH-TC SUPERCONDUCTORS
MAGNETIC PROPERTIES
MONOCRYSTALS
NEEL TEMPERATURE
NEUTRON SPECTROSCOPY
PHASE TRANSFORMATIONS
TEMPERATURE DEPENDENCE
YTTRIUM OXIDES