Magnetization in narrow ribbons: curvature effects
Magnetization in narrow ribbons: curvature effects
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DOI：
10.1088/1751-8121/aa8179
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发表时间：
2017-09-22
影响因子：
2.1
通讯作者：
Vasylkevych, Sergiy
中科院分区：
文献类型：
--
作者：
Gaididei, Yuri;Goussev, Arseni;Vasylkevych, Sergiy
带状线是一个曲面，当线段沿中心曲线沿着移动时，线段会旋转。对于线段长度远小于曲线长度的窄磁性带，静磁相互作用引起的各向异性是双轴的，具有垂直于带的难磁化轴和沿中心曲线沿着的易磁化轴。窄带的微磁能降低到一维铁磁线的微磁能，但弯曲、扭转和局部各向异性由转动速率改变。这些一般的结果被应用到两个例子，即一个螺旋带，其中的中心曲线是一条直线，和莫比乌斯带，其中的中心曲线是一个圆的线段执行180度的扭曲。在这两个例子中，对于大的正切向各向异性，基态磁化与中心曲线相切。随着切向各向异性的减小，基态磁化强度发生转变，获得垂直于中心曲线的表面内分量。对于螺旋带，转变发生在各向异性消失时，低于该各向异性，基态均匀垂直于中心曲线。莫比乌斯带的转变更为微妙;它发生在各向异性的正临界值处，低于该值，基态是不均匀的。对于螺旋带，自旋波激发关于切向态的色散规律被发现表现出由几何和磁性手征决定的不对称性。
A ribbon is a surface swept out by a line segment turning as it moves along a central curve. For narrow magnetic ribbons, for which the length of the line segment is much less than the length of the curve, the anisotropy induced by the magnetostatic interaction is biaxial, with a hard axis normal to the ribbon and an easy axis along the central curve. The micromagnetic energy of a narrow ribbon reduces to that of a one-dimensional ferromagnetic wire, but with curvature, torsion and local anisotropy modified by the rate of turning. These general results are applied to two examples, namely a helicoid ribbon, for which the central curve is a straight line, and a Mobius ribbon, for which the central curve is a circle about which the line segment executes a 180 degrees twist. In both examples, for large positive tangential anisotropy, the ground state magnetization lies tangent to the central curve. As the tangential anisotropy is decreased, the ground state magnetization undergoes a transition, acquiring an in-surface component perpendicular to the central curve. For the helicoid ribbon, the transition occurs at vanishing anisotropy, below which the ground state is uniformly perpendicular to the central curve. The transition for the Mobius ribbon is more subtle; it occurs at a positive critical value of the anisotropy, below which the ground state is nonuniform. For the helicoid ribbon, the dispersion law for spin wave excitations about the tangential state is found to exhibit an asymmetry determined by the geometric and magnetic chiralities.