颗粒状IrMn/CoFe双层膜非热训练效应的原子起源
The atomistic origin of the athermal training effect in granular IrMn/CoFe bilayers
摘要：
反铁磁材料有可能提供超快、高数据密度的自旋电子器件。一个重大的挑战是可靠的检测反铁磁体的状态，这可以通过使用交换偏置来实现。在这里，我们开发了一个原子自旋模型的非热训练效果，一个众所周知的现象，在交换偏置系统的偏见是显着减少后的第一个滞后周期。我们发现，在颗粒状薄膜的设置过程依赖于铁磁和反铁磁层之间的界面混合的存在。我们系统地研究了混合效应，发现交换偏置、开关场和双折射率都随着混合效应的增加而增加。界面自旋态是高度受挫导致系统的铁磁体的界面有序性下降。这种最初不可逆自旋的亚稳自旋结构导致大的有效交换耦合，从而大大增加了开关场。在第一个磁滞循环之后，这些亚稳态自旋下降到可逆的基态，其对于所有随后的磁滞循环是可重复的，表明该效应是真正无热的。我们的模拟提供了新的见解界面混合的作用和交换偏置系统中的亚稳自旋结构的重要性，这可能有助于反铁磁自旋电子器件的设计和优化。
英文摘要：
Anti-ferromagnetic materials have the possibility to offer ultra fast, high data density spintronic devices. A significant challenge is the reliable detection of the state of the antiferromagnet, which can be achieved using exchange bias. Here we develop an atomistic spin model of the athermal training effect, a well known phenomenon in exchange biased systems where the bias is significantly reduced after the first hysteresis cycle. We find that the setting process in granular thin films relies on the presence of interfacial mixing between the ferromagnetic and antiferromagnetic layers. We systematically investigate the effect of the intermixing and find that the exchange bias, switching field and coercivity all increase with increased intermixing. The interfacial spin state is highly frustrated leading to a systematic decrease in interfacial ordering of the ferromagnet. This metastable spin structure of initially irreversible spins leads to a large effective exchange coupling and thus large increase in the switching field. After the first hysteresis cycle these metastable spins drop into a reversible ground state that is repeatable for all subsequent hysteresis cycles, demonstrating that the effect is truly athermal. Our simulations provide new insights into the role of interface mixing and the importance of metastable spin structures in exchange biased systems which could help with the design an optimisation of antiferromagnetic spintronic devices.
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