Spin dynamics in the metallic state of YBa2(Cu0.98Zn0.02)(3)O6+x

Inelastic neutron scattering measurements have been carried out on a YBa2(C u0.98Zn0.02)(3)O6+x single crystal in both underdoped (x = 0.7) and overdop ed (x = 0.97) regimes. In the zinc substituted system, spin dynamics is dra stically changed in respect to the pure compound: (i) the "resonance peak" almost vanishes, (ii) the spin gap is filled, (iii) new antiferromagnetic e xcitations are found at low energy. These new magnetic fluctuations, which persist in the normal state, account for a local enhancement of AF correlat ions around nonmagnetic impurities. Besides, it is worth emphasizing that f eatures, not directly related to superconductivity, i.e., the contribution to the spin dynamics apart from the resonance peak and the "spin pseudo-gap " observed in the underdoped regime above T-c, coexist with the new low ene rgy magnetic fluctuations.