The optical activity refers to the rotation of the vibration plane of linearly polarized light traversing certain substances. Here we report an analogous phenomenon for spin waves (SWs) in cylindrical nanowires, whose azimuthal distribution undergoes a continuous rotation as traveling along the wire. This effect, in line with the Fresnel model of the optical activity, is attributed to different propagating speeds of two circular states (left and right handed) composing the SW modes. The SW circular birefringence observed here originates from the overall curvilinear shape of the waveguide. Moreover, the fact that an external field is able to alter the rotatory power of the nanowires is reminiscent of the Faraday magneto-optical effect.

中文翻译：

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铁磁纳米圆柱体的磁活动

光学活性是指线性偏振光穿过某些物质的振动平面的旋转。在这里，我们报道了圆柱形纳米线中自旋波（SW）的类似现象，其旋转方向的方位角分布随着沿线的传播而连续旋转。该效应与光学活性的菲涅耳模型一致，归因于组成SW模式的两个圆形状态（左手和右手）的不同传播速度。此处观察到的SW圆形双折射源于波导的整体曲线形状。而且，外部场能够改变纳米线的旋转功率的事实让人联想到法拉第磁光效应。