单畴BiFeO $_3$薄膜的磁化动力学模拟
Simulation of the Magnetization Dynamics of a Single Domain BiFeO$_3$ Thin Film
摘要：
结合极化动力学和Neel矢量动力学研究了单畴BiFeO $_3$薄膜的开关动力学。铁电极化的演化由Landau-Khalatnikov（LK）方程和Landau-Lifshitz-Gilbert（LLG）方程描述，用于模拟G型反铁磁体中反铁磁序（Neel矢量）的时间演化。这项工作从理论上证明，由于极化反转后的难磁化轴的旋转，Neel矢量可以切换180度，而弱磁化强度可以保持不变。模拟结果与Neel矢量在极化旋转过程中发生旋转的从头计算结果一致，也与我们用Landau-Ginzburg理论计算的序参量动力学结果一致.我们还发现，Neel矢量的开关时间是由偏振开关的速度，并预计将作为短的30 ps。
英文摘要：
The switching dynamics of a single-domain BiFeO$_3$ thin films is investigated through combining the dynamics of polarization and Neel vector. The evolution of the ferroelectric polarization is described by the Landau-Khalatnikov (LK) equation, and the Landau-Lifshitz-Gilbert (LLG) equations for spins in two sublattices to model the time evolution of the antiferromagnetic order (Neel vector) in a G-type antiferromagnet. This work theoretically demonstrates that due to the rotation of the magnetic hard axis following the polarization reversal, the Neel vector can be switched by 180 degrees, while the weak magnetization can remain unchanged. The simulation results are consistent with the ab initio calculation, where the Neel vector rotates during polarization rotation, and also match our calculation of the dynamics of order parameter using Landau-Ginzburg theory. We also find that the switching time of the Neel vector is determined by the speed polarization switching and is predicted to be as short as 30 ps.
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