Metastable face-centered-cubic $\mathrm{F}{\mathrm{e}}_{78}\mathrm{N}{\mathrm{i}}_{22}$ thin films are excellent candidates for focused ion beam direct writing of magnonic structures due to their favorable magnetic properties after ion-beam-induced transformation. The focused ion beam transforms the originally nonmagnetic fcc phase into the ferromagnetic bcc phase with additional control over the direction of uniaxial magnetic in-plane anisotropy and saturation magnetization. Local magnetic anisotropy direction control eliminates the need for external magnetic fields, paving the way towards complex magnonic circuits with waveguides pointing in different directions. In the present study, we show that the magnetocrystalline anisotropy in transformed areas is strong enough to stabilize the magnetization in the direction perpendicular to the long axis of narrow waveguides. Therefore, it is possible to propagate spin waves in these waveguides in the favorable Damon-Eshbach geometry without the presence of any external magnetic field. Phase-resolved microfocused Brillouin light scattering yields the dispersion relation of these waveguides in zero as well as in nonzero external magnetic fields.

中文翻译：

---

聚焦离子束直接写入制备的波导中自旋波的零场传播

亚稳面心立方 $\mathrm{F}{\mathrm{Ë}}_{78}\mathrm{ñ}{\mathrm{一世}}_{22}$薄膜由于在离子束诱导的转变后具有良好的磁性，因此是聚焦离子束直接写入大型结构的极佳候选材料。聚焦的离子束通过对单轴磁性面内各向异性和饱和磁化方向的附加控制，将原来的非磁性fcc相转变为铁磁性bcc相。局部磁各向异性方向控制消除了对外部磁场的需求，为具有指向不同方向的波导的复杂磁电电路铺平了道路。在本研究中，我们表明，转换区域的磁晶各向异性足够强，可以稳定垂直于窄波导长轴方向的磁化强度。因此，有可能以有利的Damon-Eshbach几何形状在这些波导中传播自旋波，而不会出现任何外部磁场。相分辨的微聚焦布里渊光散射产生了这些波导在零以及非零外部磁场中的色散关系。