The stability of magnetism in reduced dimensions has become a major scientific agenda in the pursuit of implementing magnetic nanostructures as functional components in spintronic devices. Methods to probe and control magnetization states of such structures in a deterministic manner include use of spin polarized currents, photon absorption, and relatively recently, electric fields that tailor magnetoelectric coupling in multiferroic based structures. In theory, a short electric pulse is able to generate localized magnetic fields that can couple to the local magnetic dipoles electrodynamically. Here, using the Landau–Lifshitz–Gilbert formalism of magnetism dynamics combined with continuum Maxwell relations, the response of a ferromagnetic permalloy nanodisc to nanosecond electric field pulses is studied. The dynamics of the magnetic order of the nanodiscs during this process are examined and discussed. Ferromagnet nanodiscs, when below a critical size and in the absence of any external field, relax to a vortex phase as the ground state due to the demagnetizing field. Simulations demonstrate that the planar chirality of such a ferromagnet nanodisc can be switched via a time-wise asymmetric electric field pulse on the order of a few ns duration that generates radially varying tangential magnetic fields. These fields couple to the vortex state of the nanodisc ferromagnet electrodynamically, revealing an effective and robust method to control chirality.

中文翻译：

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通过纳秒电脉冲在铁磁纳米结构中进行手性切换

在追求将磁性纳米结构用作自旋电子器件中的功能组件时，减小尺寸的磁性稳定性已成为一项主要的科学议程。以确定性方式探测和控制这种结构的磁化状态的方法包括使用自旋极化电流、光子吸收和相对较新的电场，这些电场在基于多铁的结构中定制磁电耦合。理论上，短电脉冲能够产生局部磁场，该磁场可以电动耦合到局部磁偶极子。在这里，使用磁动力学的 Landau-Lifshitz-Gilbert 形式主义结合连续麦克斯韦关系，研究了铁磁坡莫合金纳米圆盘对纳秒电场脉冲的响应。检查和讨论了该过程中纳米圆盘磁序的动力学。铁磁纳米盘在低于临界尺寸且没有任何外部场时，会因退磁场而弛豫到涡旋相作为基态。模拟表明，这种铁磁体纳米盘的平面手性可以通过几个 ns 持续时间的时间不对称电场脉冲进行切换，该脉冲产生径向变化的切向磁场。这些场以电动力学方式耦合到纳米圆盘铁磁体的涡旋状态，揭示了一种有效且稳健的控制手性的方法。由于退磁场而弛豫到涡旋相作为基态。模拟表明，这种铁磁体纳米盘的平面手性可以通过几个 ns 持续时间的时间不对称电场脉冲进行切换，该脉冲产生径向变化的切向磁场。这些场以电动力学方式耦合到纳米圆盘铁磁体的涡旋状态，揭示了一种有效且稳健的控制手性的方法。由于退磁场而弛豫到涡旋相作为基态。模拟表明，这种铁磁体纳米盘的平面手性可以通过几个 ns 持续时间的时间不对称电场脉冲进行切换，该脉冲产生径向变化的切向磁场。这些场以电动力学方式耦合到纳米圆盘铁磁体的涡旋状态，揭示了一种有效且稳健的控制手性的方法。