Stability of skyrmion lattices and symmetries of quasi-two-dimensional chiral magnets
Stability of skyrmion lattices and symmetries of quasi-two-dimensional chiral magnets
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DOI：
10.1103/physrevb.93.064428
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发表时间：
2016-02-24
影响因子：
3.7
通讯作者：
Kovalev, Alexey A.
中科院分区：
文献类型：
--
作者：
Guengoerdue, Utkan;Nepal, Rabindra;Kovalev, Alexey A.
最近，人们对skyrmions的实现产生了浓厚的兴趣，特别是在准二维（2D）系统中，由于减少了维度而增加了稳定性。一个稳定的skyrmion，代表最小的可实现的磁性纹理，可能是超密度磁性存储器的理想元素。在这里，我们使用最一般的形式的准二维自由能与Dzyaloshinskiii-Moriya相互作用构造从一般对称性的考虑，反映了潜在的系统。我们预测，skyrmion相位是强大的，它是存在的，即使当系统缺乏面内旋转对称性。事实上，降低对称性导致具有四重对称性和平面螺旋的涡旋-反涡旋晶格的稳定性增加，在某些情况下甚至在没有外部磁场的情况下也是如此。我们的研究结果涉及不同的六边形和正方形的细胞阶段的对称性用于实现skyrmions的材料。这将为实验实现六边形和正方形单元相提供明确的方向，并将允许工程具有不寻常属性的skyrmions。我们还预测显着差异的自旋电流引起的孤立skyrmions和晶体的自旋电流可以引起的电荷载流子或热磁振子的陀螺动力学。我们发现，在一定条件下，孤立的skyrmion可以沿着电流移动，而不会发生侧向运动，这可能对磁记忆的实现产生影响。
Recently there has been substantial interest in realizations of skyrmions, in particular in quasi-two-dimensional (2D) systems due to increased stability resulting from reduced dimensionality. A stable skyrmion, representing the smallest realizable magnetic texture, could be an ideal element for ultradense magnetic memories. Here we use the most general form of the quasi-2D free energy with Dzyaloshinskii-Moriya interactions constructed from general symmetry considerations reflecting the underlying system. We predict that the skyrmion phase is robust and it is present even when the system lacks the in-plane rotational symmetry. In fact, the lowered symmetry leads to increased stability of vortex-antivortex lattices with fourfold symmetry and in-plane spirals, in some instances even in the absence of an external magnetic field. Our results relate different hexagonal and square cell phases to the symmetries of materials used for realizations of skyrmions. This will give clear directions for experimental realizations of hexagonal and square cell phases, and will allow engineering of skyrmions with unusual properties. We also predict striking differences in gyrodynamics induced by spin currents for isolated skyrmions and for crystals where spin currents can be induced by charge carriers or by thermal magnons. We find that under certain conditions, isolated skyrmions can move along the current without a side motion which can have implications for realizations of magnetic memories.