MAGNETIC AND TRANSPORT-PROPERTIES OF ZN-DOPED YBA2CU3O7 IN THE NORMAL-STATE

Detailed resistivity and susceptibility measurements are reported on Y Ba2(Cu1-xZnx)(3)O-7 ceramics samples for 0% less than or equal to x le ss than or equal to 10% in the normal state. The superconducting tempe rature T-c(x) is found to decrease linearly with x down to 0 K at a ra te of 8.8+/-0.3 K/% up to 10% Zn in agreement with previous work. The resistivity analysis in the metallic regime shows that it is possible to tit a modified Matthiessen's law for the additivity of the impurity scattering and the thermal scattering quite similar to what is found for the ab-plane resistivity of Zn-doped single crystals. The residual resistivity linear increment of Zn in ceramic samples for x less than or equal to 5% is found to be 40+/-4 mu Omega cm/% Zn. With the first weak-localization correction to the resistivity the data can be fitte d (with the same parameters) up to x = 8% of Zn, yielding a two-dimens ional resistivity cross section of diameter 7.7 Angstrom two times lar ger than in single crystals. The same samples have been used for magne tic susceptibility determination with an improved resolution. Special care has been taken to remove (via electron paramagnetic resonance dou ble integration) the contribution from the parasitic Y2BaCuO5 ''green phase,'' which we find consistently below 1% per mole YBa2Cu3O7, indep endent of Zn level below x = 10%. We find a Curie-law term in the susc eptibility which increases linearly with Zn content. The moment define d in this way corresponds to (0.64+/-0.15)mu(beta) per Zn impurity. As sociated with this Curie term we measure a ferromagnetic Curie tempera ture T-c which decreases as the Zn concentration x increases at a rate of (57+/-6)(1-0.1x) K. The constant, temperature-independent suscepti bility chi(spin) is found to decrease linearly with increasing Zn conc entration, about two times faster than what would be expected for a lo calized model of the Zn perturbation within a single unit cell. Compar ing this decrease of chi(spin) with the increase of the Curie constant allows a consistent interpretation of the effect of Zn in [CuO2] plan e. We propose that the four near neighbor Cu to the Zn site bear a mag netic moment and are linked by a ferromagnetic interaction.