Temperature and medium structurization effect on spontaneous evolution of domains and bubbles in magnetic nanostructures

IF 1.1 Q3 PHYSICS, MULTIDISCIPLINARY
Andrzej Janutka
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引用次数: 0

Abstract

Spontaneous evolutions of domains in magnetic nanowires and of magnetic bubbles in open ferromagnetic nanolayers are investigated using micromagnetic simulations. We compare temperature dependent dynamics of domain wall (DW) systems in Permalloy (Py) nanowires and systems of chiral DWs in ultra-thin nanowires with perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI). In Py nanowires DWs collide and, in majority of cases, the collision leads to the DW annihilation in disagreement with the expectation of topological protection of sums of all the magnetic charges attached to the nanowire edges which are carried by DWs. For our purpose of discussing the DW collision in the presence of thermal excitations, we revisit the problem of field-driven collisions of DWs in Py nanowires at zero temperature. We claim that thermal fluctuations can counteract the collision-induced annihilation of DWs, thought further improvement of stabilization of domain structures is achievable via structurization of the magnetic nanowires (dividing them into grains). In PMA-DMI nanowires, thermally-excited chiral DWs can be randomly approaching or moving away while not being annihilated. A problem related to the motion of chiral DWs is the spontaneous motion of magnetic bubbles in open PMA-DMI planes. The magnetic bubbles expand or shrink to vanishing dependent on strength of the DMI interaction. Such a motion appears to be be strongly influenced by temperature and by structural discontinuities of the magnetic layer.
温度和介质结构化对磁性纳米结构中磁畴和气泡自发演化的影响
我们利用微磁模拟研究了磁性纳米线中磁畴的自发演化和开放式铁磁纳米层中磁泡的自发演化。我们比较了坡莫合金(Py)纳米线中的畴壁(DW)系统和具有垂直磁各向异性(PMA)和 Dzyaloshinskii-Moriya 相互作用(DMI)的超薄纳米线中的手性 DW 系统随温度变化的动力学。在 Py 纳米线中,DW 会发生碰撞,而在大多数情况下,碰撞会导致 DW湮灭,这与 DW 所携带的纳米线边缘所有磁荷之和的拓扑保护预期不符。为了讨论热激发下的 DW 碰撞,我们重新探讨了零温下 Py 纳米线中 DW 的场驱动碰撞问题。我们认为,热波动可以抵消碰撞引起的 DW湮灭,并认为通过磁性纳米线的结构化(将其划分为晶粒)可以进一步提高畴结构的稳定性。在 PMA-DMI 纳米线中,热激发的手性 DW 可以随机靠近或远离,同时不会湮灭。与手性 DW 运动相关的一个问题是开放式 PMA-DMI 平面中磁性气泡的自发运动。磁泡的扩大或缩小到消失取决于 DMI 相互作用的强度。这种运动似乎受到温度和磁层结构不连续性的强烈影响。
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来源期刊
Journal of Physics Communications
Journal of Physics Communications PHYSICS, MULTIDISCIPLINARY-
CiteScore
2.60
自引率
0.00%
发文量
114
审稿时长
10 weeks
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