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横向磁畴壁在梯形截面纳米带中的快速运动
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Abstract:
以往大多是以矩形截面的纳米带为载体探讨横向磁畴壁的动力学。矩形截面纳米带具有均匀的厚度，而梯形截面纳米带的中间区域厚度大于两侧。我们研究了外磁场驱动下梯形截面纳米带中的横向磁畴壁运动，并详细探讨了梯形截面纳米带中的横向磁畴壁的形貌变化。微磁模拟计算表明梯形截面的设计使得磁畴壁运动速度比在矩形截面纳米带中更快。我们发现，磁畴壁速度与梯形截面纳米带底角具有密切关系，结果表明，磁畴壁在小底角的纳米带中具有高的运动速度。我们还发现磁畴壁的速度与磁畴壁平均宽度并不成线性关系，而是与磁畴壁上下端宽度具有正比关系。除此之外，我们通过磁畴壁区域的磁矩在有效场下的旋进速度分布深入探讨了退磁场对磁畴壁高速运动的贡献。梯形截面纳米带中磁畴壁运动的研究为磁畴壁动力学中提出了新的思路。
In the past, most of the researches discuss on the dynamics of transverse magnetic domain walls were based on nanostrips with rectangular cross-section. Unlike the uniform thickness of rectan-gular cross-section nanostrips, the thickness is larger in the middle than at the sides for trapezoidal nanostrips. Transverse domain wall motion in trapezoidal nanostrips driven by external magnetic field is studied and the morphology variation of the transverse magnetic domain walls is discussed in detail. The micromagnetic simulation results show that the velocity of magnetic domain wall motion is faster than that of rectangular nanostrips due to the design of trapezoidal cross-section. It is found that the magnetic domain wall velocity is closely related to the base angle of the trapezoidal cross-section. As a result, the magnetic domain wall has a high velocity in the nanostrips with small base angle. We find that the velocity of magnetic domain wall is not linearly related to the average width of magnetic domain wall, but is proportional to the width of the upper and lower ends of the magnetic domain wall. In addition, the contribution of demagnetization to the fast motion of the domain wall is discussed through the precession speed distribution of the magnetization in the domain wall region under the effective field. The study of the magnetic domain wall motion in trapezoidal cross-section nanostrips provides a new idea for the magnetic domain wall dynamics.
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