标题： 磁性珠子在条纹铁氧体石榴石薄膜上方的棘轮效应 显示英文标题

标题： Ratchet effects for paramagnetic beads above striped ferrite-garnet films

摘要： 我们计算了由铁氧体-石榴石薄膜的条纹畴图案操控的小型磁性珠子的运动。 开发了一个珠子在薄膜上方液体中的运动模型，并用于寻找棘轮解，其中当外部场被周期性调制时，珠子会沿一个方向获得净相干运动。 我们考虑了三种情况。 首先，棘轮情况，其中所有珠子都向同一方向移动。 其次，高度依赖的棘轮，其中不同高度的珠子向相反方向移动。 这种情况可用于分离不同大小的珠子，如在J. Phys. Chem. B 112, 3833 (2008)中所考虑的。 第三，我们描述了如何通过改变施加场的振幅来调节分离阈值。 最后，我们描述了一种伪棘轮，其中外部调制不是周期性的，棘轮方向会周期性地变化。 显示英文摘要

摘要： We calculate the motion of a small paramagnetic bead which is manipulated by the stripe domain pattern of a ferrite-garnet film. A model for the bead's motion in a liquid above the film is developed and used to look for ratchet solutions, where the bead acquires net coherent motion in one direction when the external field is modulated periodically. We consider three cases. First, the ratchet, where the beads all go in the same direction. Second, the height dependent ratchet, where beads at different heights go in opposite direction. This case can be used to separate beads of different sizes, as considered in J. Phys. Chem. B 112, 3833 (2008). Third, we describe how the separation threshold can be tuned by changing the amplitude of the applied field. Finally, we describe a pseudo ratchet, where the external modulation is not periodic and the ratchet changes direction periodically.