Time resolved studies of coherent spin waves in ferro/antiferromagnetically coupled exchange bias systems

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The goals of this proposal are systematic time-resolved studies of ultrafast magnetization reversal mechanisms in exchange bias systems using all optical pump-probe spectroscopy. This ultrafast optical approach implies the prospect of inducing and investigating basic magnetization switching and relaxation phenomena with the exchange coupled system impulsively driven by the absorbed photons on ultrafast time scales. In a first focus, the asymmetric magnetization reversal as was observed in Fe/FeF2 by neutron reflectometry shall be investigated in the time domain. In particular, we want to explore switching speed as well as precessional switching dynamics on the relevant magnetization reversal mechanisms, such as coherent magnetization rotation and domain wall propagation. In a second focus, the role of the antiferromagnetic spin structure on the magnetization reversal mechanisms in Co/CoO bilayers shall be studied. Here, the antiferromagnetic spin and domain structure can be controlled by intentionally introducing Co deficiencies (Co1-yO) in the volume of the antiferromagnetic layer. These deficiencies are known to cause and control exchange bias within the domain state model. Beside fundamental questions regarding the reversal mechanisms, we want to investigate whether the spin dynamics at the ferro-/antiferromagnetic interface can directly be influenced and modified by ultrafast optical pumping of spins near defects in the antiferromagnetic subsystem.