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Title: NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}

Abstract

We report a set of nuclear quadrupole resonance (NQR) measurements including a spin-echo double-resonance (SEDOR) experiment which provides convincing evidence that the additional chain Cu NQR line in Ca-substituted YBa{sub 2}Cu{sub 4}O{sub 8} does stem from chain Cu sites disturbed by the {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions. From an analysis of signal intensities we conclude that {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions, responsible for the additional line, substitute Y{sup 3+}. At high Ca doping, the concentration of the substituted Y sites, {ital x}{sup {prime}}, is appreciably smaller than the nominal Ca concentration, {ital x}. Since it is {ital x}{sup {prime}} which is responsible for a direct increase of the hole charge-carrier concentration, {ital n}, effects connected with the increase of {ital n} such as the planar Cu spin-lattice relaxation rate, the NQR frequency, and the magnetic shift are only weakly dependent on {ital x}. Thus, the substantial increase of {ital T}{sub {ital c}} with {ital x} suggests that, besides the increase of {ital n}, other effects have to play a role in the {ital T}{sub {ital c}} enhancement. One such effect might be the opening of the spin pseudogap. At 150 K, both the main and additional Cu NQR lines in nominal YBa{sub 1.9}Ca{sub 0.1}Cu{submore » 4}O{sub 8} show distinctly anomalies not seen in pure YBa{sub 2}Cu{sub 4}O{sub 8} that point out the Ca doping induced structural phase transition recently observed in specific-heat, elastic-neutron-scattering, and x-ray-diffraction measurements. {copyright} {ital 1996 The American Physical Society.}« less

Authors:
; ;  [1]
  1. Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland)
Publication Date:
OSTI Identifier:
279472
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter
Additional Journal Information:
Journal Volume: 53; Journal Issue: 6; Other Information: PBD: Feb 1996
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; BARIUM OXIDES; NUCLEAR MAGNETIC RESONANCE; NUCLEAR QUADRUPOLE RESONANCE; YTTRIUM OXIDES; COPPER OXIDES; CALCIUM ADDITIONS; CALCIUM IONS; CRYSTAL DEFECTS; CRYSTAL-PHASE TRANSFORMATIONS; CUPRATES; HIGH-TC SUPERCONDUCTORS; HOLES; MAGNETIC SUSCEPTIBILITY; SPIN ECHO; SPIN-LATTICE RELAXATION; SUBSTOICHIOMETRY; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K; TRANSITION TEMPERATURE

Citation Formats

Mali, M, Roos, J, and Brinkmann, D. NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}. United States: N. p., 1996. Web. doi:10.1103/PhysRevB.53.3550.
Mali, M, Roos, J, & Brinkmann, D. NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}. United States. doi:10.1103/PhysRevB.53.3550.
Mali, M, Roos, J, and Brinkmann, D. Thu . "NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}". United States. doi:10.1103/PhysRevB.53.3550.
@article{osti_279472,
title = {NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}},
author = {Mali, M and Roos, J and Brinkmann, D},
abstractNote = {We report a set of nuclear quadrupole resonance (NQR) measurements including a spin-echo double-resonance (SEDOR) experiment which provides convincing evidence that the additional chain Cu NQR line in Ca-substituted YBa{sub 2}Cu{sub 4}O{sub 8} does stem from chain Cu sites disturbed by the {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions. From an analysis of signal intensities we conclude that {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions, responsible for the additional line, substitute Y{sup 3+}. At high Ca doping, the concentration of the substituted Y sites, {ital x}{sup {prime}}, is appreciably smaller than the nominal Ca concentration, {ital x}. Since it is {ital x}{sup {prime}} which is responsible for a direct increase of the hole charge-carrier concentration, {ital n}, effects connected with the increase of {ital n} such as the planar Cu spin-lattice relaxation rate, the NQR frequency, and the magnetic shift are only weakly dependent on {ital x}. Thus, the substantial increase of {ital T}{sub {ital c}} with {ital x} suggests that, besides the increase of {ital n}, other effects have to play a role in the {ital T}{sub {ital c}} enhancement. One such effect might be the opening of the spin pseudogap. At 150 K, both the main and additional Cu NQR lines in nominal YBa{sub 1.9}Ca{sub 0.1}Cu{sub 4}O{sub 8} show distinctly anomalies not seen in pure YBa{sub 2}Cu{sub 4}O{sub 8} that point out the Ca doping induced structural phase transition recently observed in specific-heat, elastic-neutron-scattering, and x-ray-diffraction measurements. {copyright} {ital 1996 The American Physical Society.}},
doi = {10.1103/PhysRevB.53.3550},
journal = {Physical Review, B: Condensed Matter},
number = 6,
volume = 53,
place = {United States},
year = {1996},
month = {2}
}