Exchange bias in a spin glass

R. Mathieu

The hysteresis curves (representing magnetic-field dependent magnetization measurements) of ferromagnetic materials may be shifted away from the zero-magnetic field axis. This exchange-bias phenomenon, employed in spintronic devices, is usually associated with the exchange anisotropy created in artificial structures at the interface between antiferromagnetic (AFM) and ferromagnetic (FM) materials. However there are materials which exhibit exchange bias without having a clear AFM/FM interface, as for example spin glasses. Spin glasses are magnetic systems without long-range magnetic order. Due to magnetic disorder and frustration, these systems are always out of equilibrium, and their spin configuration is endlessly rearranging itself.
In this seminar, I will review the peculiar magnetic properties exhibited by spin glasses, such as aging, memory and rejuvenation effects. A detailed study of the exchange bias in a Cu(Mn) spin glass will then be presented, and compared to the conventional exchange-bias systems.

Work performed together with Matthias Hudl and Prof. Per Nordblad.
www2.angstrom.uu.se/magnetism/

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