Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 5: Superconductivity - Mechanisms, Phase Diagram, Competing Order

TT 5.2: Vortrag

Freitag, 4. März 2005, 18:15–18:30, TU H104

Inhomogeneous charge and spin order in electron-doped high-T_c cuprate superconductors — •H.-H. Klauss¹, D. Baabe¹, H. Luetkens², D. Mienert¹, P. Adelmann³, Y. Krockenberger⁴, L. Alff⁴, M. Naito⁵, and F.J. Litterst¹ — ¹IMNF, TU Braunschweig, Germany — ²PSI, Villigen, Schweiz — ³IFP, FZ Karlsruhe, Germany — ⁴WMI, TU München, Germany — ⁵NTT, Atsugi, Japan

We investigated the relevance of inhomgeneous charge and spin order in the electron-doped high-T_c superconductors (Nd,Pr)_2−yCe_yCuO₄ with 0.05 ≤ y ≤ 0.125 by means of muon spin relaxation (µ⁺SR). In this doping range the samples show long- range antiferromagnetic order below T ≈ 100 K. In all samples we found inhomogeneous local field distributions, which are consistent with an electronic phase separation on a nanometer length scale. This suggests, in addition to similar results in hole-doped cuprates, that this phenomenon is of general relevance for the physics of cuprate superconductors. We also studied the magnetic and superconducting properties of a 20 nm Ag/300 nm La_1.9Ce_0.1CuO₄ (LCCO) heterostructure by means of low-energy µ⁺SR. For temperatures below T = 90 K, the stoichiometrically homogeneous LCCO film exhibits a magnetic layer at the interface to the Ag capping. Energy-dependent low-energy µ⁺SR reveals that the thickness of this magnetic layer continuously increases from 0 nm to 50 nm with decreasing temperature and that it persists below the superconducting transition at T_c = 28 K. In an applied magnetic field, the LCCO film shows Meissner screening with a magnetic penetration depth of the order of 350 nm proving the coexistence of bulk superconductivity and magnetism in the same sample.