Deterministic switching of ferromagnetism at room temperature using an electric field
Deterministic switching of ferromagnetism at room temperature using an electric field
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DOI：
10.1038/nature14004
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发表时间：
2014-12-18
期刊：
影响因子：
64.8
通讯作者：
Ramesh, R.
中科院分区：
文献类型：
--
作者：
Heron, J. T.;Bosse, J. L.;Ramesh, R.
多铁性材料的技术吸引力是用电场控制磁性的能力（1-3）。为了使装置有用，这种控制必须在室温下实现。唯一在室温下表现出明确磁电耦合的单相多铁性材料是BiFeO 3（参考文献4和5）。它的弱铁磁性来自于Dzyaloshinskiii-Moriya（DM）相互作用（6-9）引起的反铁磁性排列自旋的倾斜。先前的理论考虑了热力学基态的对称性，并得出结论，禁止通过铁电极化直接180度切换DM矢量（10，11）。相反，我们研究了开关过程的动力学，这是以前在理论工作中没有考虑过的（10-12）。在这里，我们使用室温下的电场展示了DM矢量和倾斜力矩的确定性反转。第一性原理计算表明，开关动力学有利于两步开关过程。在每一步中，DM矢量和极化耦合，从而使磁化的180度确定性切换成为可能，与实验观察一致。我们利用这种开关，以证明在室温下的自旋阀器件的节能控制。每单位面积所需的能量大约比自旋转移扭矩转换所需的能量小一个数量级（13，14）。考虑到DM相互作用是单相多铁性和磁电学的基础（3，9），我们的研究结果提出了设计磁电开关的方法，并为纳米级，低能耗，非易失性磁电子学定制技术相关功能。
The technological appeal of multiferroics is the ability to control magnetism with electric field(1-3). For devices to be useful, such control must be achieved at room temperature. The only single-phase multiferroic material exhibiting unambiguous magnetoelectric coupling at room temperature is BiFeO3 (refs 4 and 5). Its weak ferromagnetism arises from the canting of the antiferromagnetically aligned spins by the Dzyaloshinskii-Moriya (DM) interaction(6-9). Prior theory considered the symmetry of the thermodynamic ground state and concluded that direct 180-degree switching of the DM vector by the ferroelectric polarization was forbidden(10,11). Instead, we examined the kinetics of the switching process, something not considered previously in theoretical work(10-12). Here we show a deterministic reversal of the DM vector and canted moment using an electric field at room temperature. First-principles calculations reveal that the switching kinetics favours a two-step switching process. In each step the DM vector and polarization are coupled and 180-degree deterministic switching of magnetization hence becomes possible, in agreement with experimental observation. We exploit this switching to demonstrate energy-efficient control of a spin-valve device at room temperature. The energy per unit area required is approximately an order of magnitude less than that needed for spin-transfer torque switching(13,14). Given that the DM interaction is fundamental to singlephase multiferroics and magnetoelectrics(3,9), our results suggest ways to engineer magnetoelectric switching and tailor technologically pertinent functionality for nanometre-scale, low-energy-consumption, non-volatile magnetoelectronics.