Local Probe Studies of high-Tc Superconductors and CMR Oxides Using Radioactives Isotopes

V. S. Amaral 2Joao P. Araujo 3A.M.L. Lopes 2,5E. Rita 1,5J. G. Correia 1,5U. Wahl 1P. B. Tavares 4ISOLDE Collaboration 5

1. Instituto Técnológico Nuclear (ITN), Sacavém 2686, Portugal
2. Universidade de Aveiro, Departamento de Fisica and CICECO (UA), Campus de Santiago, Aveiro 3810-193, Portugal
3. Departamento de Fisica and IFIMUP, Universidade do Porto (UP), Rua do Campo Alegre, 687, Porto 4169-007, Portugal
4. Departamento de Química, Universidade de Trás-os-Montes e Alto Douro (UTAD), Vila Real 5001-911, Portugal
5. European Centre for Nuclear Research (CERN), Geneva CH1211, Switzerland

Abstract

The route to induce high-Tc superconductivity and CMR relies on the doping of the parent antiferromagnetic insulator compound which is commonly performed by partial or total replacement of elements, incorporation of vacancies and/or oxygen. In such intrinsically disordered systems, microscopic phenomena like point or extended defects or the lattice site of dopants are known to play a crucial role on their electric and magnetic properties, pointing to the existence of key microscopic phenomena for which atomic-scale studies are highly desirable.Nuclear hyperfine techniques are extremely useful in providing atomic scale information on the probe-element interactions with the lattice host. In particular, the measurement of the electric field gradient (EFG) and/or the magnetic hyperfine fields (MHF) at specific probe-element nuclei provides direct information on the local charge distribution and/or local spin density transfer, thus providing a fingerprint of the lattice site and the specific point defects located at the probe's neighbourhood. In this way, nuclear techniques using radioactive isotopes like γ-γ, e--γ Perturbed Angular Correlations (PAC) and the Electron Emission Channelling (EC) techniques were used to provide relevant information on the electronic environment and the lattice location of specific elements or probes on high-Tc superconductors and CMR oxides. We present studies on: a) Unusual properties of cadmium doped manganites b) Mercury doping of YBa2Cu3O7 high-Tc superconductor c)Oxygen doping of Hg-based high-Tc superconductors and structure of oxygen defects.

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Presentation: oral at E-MRS Fall Meeting 2003, Symposium D, by Joao P. Araujo
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-28 05:03
Revised:   2009-06-08 12:55
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