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

该方案的目标是利用全光抽运-探测光谱技术对交换偏置系统中的超快磁化反转机制进行系统的时间分辨研究。这种超快光学方法暗示了在超快时间尺度上利用吸收光子脉冲驱动的交换耦合系统诱导和研究基本磁化翻转和弛豫现象的前景。在第一个焦点中，将在时域中研究通过中子反射计在Fe/FeF 2中观察到的不对称磁化反转。特别是，我们要探索开关速度以及旋进开关动力学的相关磁化反转机制，如相干磁化旋转和畴壁传播。在第二个重点，反铁磁自旋结构的作用，在Co/CoO双层的磁化反转机制进行了研究。这里，反铁磁自旋和畴结构可以通过在反铁磁层的体积中有意地引入Co缺陷（Co 1-yO）来控制。已知这些缺陷会导致和控制域状态模型内的交换偏置。除了关于反转机制的基本问题之外，我们还想研究铁/反铁磁界面处的自旋动力学是否可以直接受到反铁磁子系统中缺陷附近自旋的超快光泵浦的影响和修改。

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.