Magnetic properties of the overdoped superconductor La{sub 2-x}Sr{sub x}CuO{sub 4} with and without Zn impurities

The magnetic properties of the Zn-substituted overdoped high-T{sub c} superconductor La{sub 2-x}Sr{sub x}Cu{sub 1-y}Zn{sub y}O{sub 4} have been studied by magnetization measurements and neutron scattering. Magnetization measurements reveal that for Zn-free samples with x{>=}0.22 a Curie term is induced in the temperature dependence of the magnetic susceptibility implying the existence of local paramagnetic moments. The induced Curie constant corresponds to a moment of 0.5 {mu}{sub B} per additional Sr{sup 2+} ion that exceeds x=0.22. Zn substitution in the overdoped La{sub 2-x}Sr{sub x}CuO{sub 4} also induces a Curie term that corresponds to 1.2 {mu}{sub B} per Zn{sup 2+} ion, simultaneously suppressing T{sub c}. The relationship between T{sub c} and the magnitude of the Curie term for Zn-free La{sub 2-x}Sr{sub x}CuO{sub 4} with x{>=}0.22 and for Zn-substituted La{sub 2-x}Sr{sub x}CuO{sub 4} with x=0.22 are closely similar. This signifies a general competitive relationship between the superconductivity and the induced paramagnetic moment. Neutron scattering measurements show that Zn substitution in overdoped La{sub 2-x}Sr{sub x}CuO{sub 4} anomalously enhances the inelastic magnetic scattering spectra around the ({pi},{pi}) position, peaking at {omega}{approx}7 meV. These facts are discussed on the basis of a 'swiss-cheese' model of Zn-substituted systems as well as a microscopic phase separation scenario in themore » overdoped region indicated by muon-spin-relaxation measurements.« less