Model of nuclear relaxation in YBa sub 2 Cu sub 3 O sub 7 minus. delta

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.11260· OSTI ID:7155108

Cox, D L; Trees, B R ^[1]

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1. Department of Physics, The Ohio State University, 174 West 18th Avenue, Columbus, Ohio 43210 (US)

We examine nuclear spin-lattice relaxation rates (1/{ital T}{sub 1}) at copper (Cu), oxygen (O), and yttrium (Y) sites in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. We use a two-hole band model consisting of strongly Heisenberg superexchange coupled spins ({ital S}=1/2) on Cu sites that are exchange coupled with strength {ital J}{sub {ital p}{ital d}} to itinerant oxygen holes introduced by doping. The Cu(1) (chain) spins are modeled by one-dimensional Heisenberg chains; the Cu(2) (planar) spins are modeled by two-dimensional Schwinger boson mean-field theory. We first consider the limit of {ital J}{sub {ital p}{ital d}}=0 to explain the following: (i) qualitatively the superlinear behavior of 1/{ital T}{sub 1} versus temperature {ital T} on Cu(1) (chain sites) in terms of their quasi-one-dimensional character, (ii) the insufficiency of arguments producing a {ital T}{sup 1/2} temperature dependence on Cu(2) (planar) sites due to the vastly stronger temperature dependence of the antiferromagnetic fluctuations, (iii) the development of an anomaly in 1/{ital T}{sub 1}{ital T} similar to experimental data due to anisotropy and/or quantum disorder induced spin gaps,'' (iv) the need to produce some recalibration of estimates of transferred Cu(2) to Cu nuclear coupling with proper account of intersite fluctuations, and (v) the dramatic reduction of the transferred Cu spin fluctuation contribution to 1/{ital T}{sub 1} on Y and O(2,3) (planar) sites arising from form-factor effects (and hence the observation of metallic Korringa behavior at these nuclei). Next, we demonstrate formally that for finite values of {ital J}{sub {ital p}{ital d}} the low-temperature proportionality of O(2,3) and Cu(2) rates may be understood as arising from coupling of Cu- and O-hole spin susceptibilities in the presence of a Cu(2) anisotropy or spin gap.

• OSTI ID: 7155108
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:16; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
ANTIFERROMAGNETISM
BAND THEORY
BARIUM COMPOUNDS
BARIUM OXIDES
BOSONS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL MODELS
EXCHANGE INTERACTIONS
FLUCTUATIONS
HEISENBERG MODEL
HOLES
INTERACTIONS
MAGNETIC RESONANCE
MAGNETISM
MATHEMATICAL MODELS
NUCLEAR MAGNETIC RESONANCE
OXIDES
OXYGEN COMPOUNDS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
TYPE-II SUPERCONDUCTORS
VARIATIONS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES