Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: Symposium: Frontiers of Surface Sensitive Electron Microscopy II (Invited Speakers: Jürgen Kirschner, Liviu Chelaru, Michael Bauer, Claus Schneider)

O 63.7: Vortrag

Donnerstag, 28. Februar 2008, 12:00–12:15, MA 043

Microscopic investigation of exchange bias in Ni/FeMn bilayers — •Florian Kronast, Joachim Schlichting, Ruslan Ovsyannikov, Florin Radu, Shrawan Mishra, Hermann Dürr, and Wolfgang Eberhardt — BESSY GmbH , Berlin, Germany

The exchange interaction at the interface between an antiferromagnet (AF) and a ferromagnet (FM) is responsible for exchange bias, i.e. an unidirectional anisotropy seen by a shift of the FM hysteresis loop. Element specific magnetic imaging by photoelectron emission microscopy (PEEM) is a powerful tool to investigate the arrangement of magnetic moments near the interface. Recent PEEM studies of Co/FeMn bilayers demonstrated the presence of uncompensated Fe and Mn spins at the AF interface [1]. But their influence on the exchange bias could not be revealed so far.

Here we report on the first attempt to investigate the magnetic interface coupling in Ni/FeMn bilayers by PEEM using applied magnetic fields during imaging. A magnetic yoke was especially designed to minimize the deflection of photoelectrons by the Lorentz force. We studied the domain structure in the FM layer and the arrangement of magnetic moments at the interface of the AF as a function of magnetic field. Our main objective was to obtain a nano-scale image of the exchange bias strength in Ni/FeMn bilayers and correlate this with the magnetic arrangement of uncompensated spins at the AF interface. Saturating the FM layer by the applied magnetic field we can separate pinned and unpinned spins at the interface of the AF which are expected to be essential for the exchange bias. [1] PRB 75, 224406 (2007)