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MA: Fachverband Magnetismus
MA 4: Magnetic Coupling Phenomena/ Exchange Bias
MA 4.4: Vortrag
Montag, 14. März 2011, 11:45–12:00, HSZ 403
Exchange bias effects studied by transport measurements in Co/CoO micro and nanowires — •Francis Bern, José Barzola-Quiquia, and Pablo Esquinazi — Division of Superconductivity and Magnetism, University of Leipzig, D-04103 Leipzig
In-plane and out-of-plane magnetoresistance (MR) of oxidized Cobalt nanowires with widths of 300nm to 5µm in a variety of geometries was measured in the temperature range from 2.5K to 250K and in fields up to ±8T. Formation of CoO on the surface leads to exchange bias effects that were studied by MR measurements. The wires were prepared with different widths resulting in different coercive fields. This provides us with the possibility to control locally the direction of unidirectional anisotropy in zero cooling field. Besides the well known HEB effect resulting in a horizontal shift of the hysteresis loop strong asymmetries and a Rshift= R(H)-R(-H) in the saturated field region were observed. Measurements of Rshift indicate a new approach to examine the exchange bias phenomenon on microscopic scale, and were compared to a model developed within a Stoner-Wohlfarth approach.