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MA: Fachverband Magnetismus

MA 4: Magnetic Coupling Phenomena/ Exchange Bias

MA 4.1: Talk

Monday, March 14, 2011, 11:00–11:15, HSZ 403

Imaging of exchange bias on the nm length scale — •Julia Herrero-Albillos¹, Florian Kronast¹, Logane Bismaths¹, Christian Papp², and Charles Fadley³ — ¹Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany — ²Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Germany — ³Department of Physics, University of California Davis and Materials Sciences Division Lawrence Berkeley National Laboratory, USA

The direct exchange interaction at the interface between an antiferromagnet (AF) and a ferromagnet (FE) allows tailoring magnetic properties like the coercitivity and the exchange bias. At the S-PEEM in BESSY we have grown in-situ Co/FeMn bi-layer films in order to investigate the domain structure in the FE Co layer and the arrangement of magnetic moments at the interface of the AF FeMn layer. Exploiting the unique capabilities of element specific magnetic imaging by X-PEEM and a sample holder designed for imaging under applied magnetic fields (H), we were able to study the evolution of magnetic domains in the Co layer as a function of H and its layer thickness. Maps of the local exchange bias are obtained from the analysis of the space-resolved hysteresis loop images taken at different H. For samples where the FE domains are stabilized either by the AF layer or the application H upon cooling, an enhanced coercivity and exchanged bias was obtained for a critical Co thickness. In the case of Co grown without field and before the deposition of the AF, only a small exchange bias was observed which, nonetheless, mimics the as grown Co magnetization, i.e. the FE domains have been imprinted on the AF layer.