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TT: Tiefe Temperaturen

TT 11: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 11.8: Vortrag

Dienstag, 28. März 2006, 11:30–11:45, HSZ 301

Imaging of Domain Superconductivity in a Ferromagnet-Superconductor-Bilayer by Low Temperature Scanning Laser Microscopy — •H. Eitel¹, J. Fritzsche², R. Szymczak³, V.V. Moshchalkov², R. Kleiner¹, and D. Koelle¹ — ¹Physikalisches Institut - Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany — ²Nanoscale Superconductivity and Magnetism Group, K.U. Leuven, Belgium — ³Polish Academy of Science, Institute of Physics, Warsaw, Poland

We present a spatially resolved analysis of the electric transport properties of a superconductor-ferromagnet hybrid system. This hybrid consists of a Nb thin film micro bridge on top of a PbFe₁₂O₁₉ single crystal whose easy axis is perpendicular to the plane of the Nb film. We used low-temperature scanning laser microscopy (LTSLM) to image regions of Nb at the transition temperature T_c as a function of temperature T and applied magnetic field H_app, up to the saturation field H_s of PbFe₁₂O₁₉. The LTSLM images give direct evidence that so called ”domain superconductivity” in Nb is induced due to the magnetic domain structure of the ferromagnet. I.e., T_c of the Nb film is larger in areas above a magnetic domain with magnetization direction opposite to H_app, because in those areas the Nb experiences a reduced total magnetic field. By changing H_app from zero up to H_s, the evolution of the magnetic domain structure can be traced by LTSLM. The correlation of the LTSLM images with integral R(T,H) data obtained during LTSLM imaging and with room temperature AFM-images of the PbFe₁₂O₁₉ domain structure and its dependence on H_ext will be discussed.