Magnetic and transport properties of Zn-doped YBa2Cu3O7 in the normal state

Abstract

Detailed resistivity and susceptibility measurements are reported on ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Zn}}_{\mathit{x}}$ ${)}_3$ ${\mathrm{O}}_7$ ceramics samples for 0%≤x≤10% in the normal state. The superconducting temperature ${\mathit{T}}_{\mathit{c}}$(x) is found to decrease linearly with x down to 0 K at a rate 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 fit 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≤5% is found to be 40±4 μΩ cm/% Zn. With the first weak-localization correction to the resistivity the data can be fitted (with the same parameters) up to x=8% of Zn, yielding a two-dimensional resistivity cross section of diameter 7.7 Å two times larger than in single crystals. The same samples have been used for magnetic susceptibility determination with an improved resolution. Special care has been taken to remove (via electron paramagnetic resonance double integration) the contribution from the parasitic ${\mathrm{Y}}_2$ ${\mathrm{BaCuO}}_5$ ‘‘green phase,’’ which we find consistently below 1% per mole ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$, independent of Zn level below x=10%.