It is known that a Bloch domain wall in an anisotropic ferromagnet is transparent to spin waves. This result is derived by approximating the dipolar interaction between magnetic moments by an effective anisotropy interaction. In this paper we study the scattering of spin waves by a domain wall, taking into account the full complexity of the dipolar interaction, treating it perturbatively in the distorted wave Born approximation. Due to the peculiarities of the dipolar interaction, the implementation of this approximation is not straightforward. The difficulties are circumvented here by realizing that the contribution of the dipolar interaction to the spin wave operator can be split into two terms: (i) an operator that commutes with the spin wave operator in the absence of dipolar interaction and (ii) a local operator suitable to be treated as a perturbation in the distorted wave Born approximation. We analyze the scattering parameters obtained within this approach. It turns out that the reflection coefficient does not vanish in general, and that the transmitted waves suffer a lateral shift which is of order one (not infinitesimal) even at nearly normal incidence. This lateral shift can be greatly enhanced by making the spin wave go through an array of well-separated domain walls. The outgoing spin wave will not be appreciably attenuated by the scattering at the domain walls since the transmission coefficient is very close to 1 at nearly normal incidence. This effect may be very useful to control the spin waves in magnonic devices.

中文翻译：

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布洛赫畴壁对自旋波的散射：偶极相互作用的影响

众所周知，各向异性铁磁体中的布洛赫畴壁对自旋波是透明的。该结果是通过通过有效的各向异性相互作用来近似磁矩之间的偶极相互作用而得出的。在本文中，我们研究了畴壁对自旋波的散射，考虑到偶极相互作用的全部复杂性，在扭曲波 Born 近似中对其进行微扰处理。由于偶极相互作用的特殊性，这种近似的实现并不简单。通过意识到偶极相互作用对自旋波算子的贡献可以分为两个方面，这里的困难被规避了：(i) 在没有偶极相互作用的情况下与自旋波算子对易的算子和 (ii) 适合被视为扭曲波 Born 近似中的扰动的局部算子。我们分析了在这种方法中获得的散射参数。事实证明，反射系数通常不会消失，并且即使在接近垂直入射的情况下，透射波也会发生一阶（不是无穷小）的横向偏移。通过使自旋波穿过一系列分离良好的畴壁，可以大大增强这种横向偏移。出射的自旋波不会被畴壁处的散射明显衰减，因为透射系数在接近垂直入射时非常接近 1。这种效应对于控制磁振装置中的自旋波可能非常有用。