Regensburg 2004 – wissenschaftliches Programm

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MA: Magnetismus

MA 22: Spinabh
ängiger Transport I

MA 22.1: Vortrag

Donnerstag, 11. März 2004, 12:15–12:30, H22

Imaging tunnel magnetoresistance related to magnetic microdomain distribution along a La_2/3Ca_1/3MnO₃ grain boundary — •Wagenknecht Michael¹, Timo Nachtrab¹, Markus Turad¹, Dieter Koelle¹, Reinhold Kleiner¹, Jan Boris Philipp², and Rudolf Gross² — ¹Physikalisches Institut-Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany — ²Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner Straße 8, D-85748 Garching, Germany

We present electrical transport measurements across an artificial grain boundary in a La_2/3Ca_1/3MnO₃ thin film grown on a 24^∘ bicrystal SrTiO₃ substrate. In the ferromagnetic-metallic phase below T_c ≈ 220 K the grain boundary acts as a tunneling barrier. Applying an in-plane magnetic field up to 40 mT parallel to the grain boundary we observe several discrete jumps in the magnetoresistance across the barrier. We explain the resistance steps by formation of microdomains along the grain boundary. Using low temperature laser scanning microscopy allows us to image the tunnelling conductance distribution along the grain boundary for the discrete resistance steps. By this we are able to map the fraction of parallel/antiparallel aligned microdomains versus magnetic field and to correlate the domain distribution with the overall resistance across the grain boundary.