Nuclear quadrupole resonance study of magnetic and nonmagnetic impurities inYBa2Cu4O8

Abstract

Cu nuclear quadrupole resonance has been used to investigate the effect of nonmagnetic Zn and magnetic Ni impurities on the normal-state properties in the underdoped ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{4}{\mathrm{O}}_{8}$ superconducting cuprate. We find that, in contrast to measurements on optimally doped ${\mathrm{YBa}}_{2}({\mathrm{Cu}}_{1\ensuremath{-}z}{\mathrm{Zn}}_{z}{)}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}},$ there is no evidence of a complete local suppression of the antiferromagnetic correlations about the Zn impurity. There is also no evidence of Ni locally affecting the antiferromagnetic correlations. These results have important implications for superconductivity theories that assume a local suppression of the antiferromagnetic and superconducting correlations.