<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Y</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>89</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>NMR evidence for a fermi-liquid behavior in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>
Abstract
We report NMR shift \ensuremath{\Delta}K and ${T}_{1}$ data of $^{89}\mathrm{Y}$ taken from 77 to 300 K in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathrm{x}}$ for 0.35<x<1, from the insulating to the metallic state. A Korringa law and therefore a Fermi-liqud picture is found to apply for the spin part ${K}_{s}$ of \ensuremath{\Delta}K. The spin contribution ${\ensuremath{\chi}}_{s}$(x,T) to ${\ensuremath{\chi}}_{m}$ is singled out, as the T variation of \ensuremath{\Delta}K scales linearly with the macroscopic susceptibility ${\ensuremath{\chi}}_{m}$. This implies that Cu(3d) and O(2p) holes do not have independent degrees of freedom. Their hybridization, which has a \ensuremath{\sigma} character, hardly varies with doping. These results put severe constraints on theoretical models of high-${T}_{c}$ cuprates.
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