MAGNETIC-PROPERTIES OF THE NORMAL-STATE OF YBA2CU3-XLIXOZ

Resistivity and magnetization measurements were carried out on two ser ies of YBa2Cu3-xLixOy compounds annealed under either air or oxygen at mosphere, with 0 < x(Li) < 0.6. A decrease of 1.14 oxygen. Li mol(-1) is observed. All the samples are orthorhombic and remain in the metall ic range. The materials obey a Curie or Curie-Weiss law. As long as x( Li) < 0.30, lithium is assumed to substitute for copper of the chains; the d rho/dT slope is positive and T-c decreases very slowly in a qua siplateau. If the observed effective magnetic moment is assumed to be carried by lithium, this moment is constant and equal to 1.1 mu(B) /Li +; if it is assumed to be carried by all the copper ions, it increases at a rate of congruent to 1.2 mu(B)/Li [i.e., 1 mu(B)/lost O--]. When x(Li) > 0.30, lithium probably occupies a second site; the resistivit y is characterized by a metal-like behavior above 100 K and by a logar ithmic increase below 100 K; the effective moment increases up to p(ef f)/Li= 1.6 mu(B) or p(eff)/Cu = 0.8 mu(B). The spin susceptibility dec reases as a function of the doping level showing the gradual transitio n from a YBCO7-type behavior towards a still metallic but rather YBCO6 .5-like material. The Cu(1) substitution by Li leads to a gradual deco upling of the planes and to a weak localization of the charge carriers , in that case, the magnetic moments induced by the doping do not seem to have any influence on the T-c behavior at least when x(Li) < 0.30. (C) 1998 American Institute of Physics. [S0021-8979(98)03914-0].