The interest in artificial magnetic media such as magnonic crystals increased substantially in recent years due to their potential applications in information processing at microwave frequencies. The main features of these crystals are the presence of band gaps in the spin-wave spectra, usually formed due to Bragg reflections of spin-waves on the artificially created periodic structures. Here, we study spin-wave propagation in longitudinally magnetized width- and thickness-modulated yttrium iron garnet waveguides by means of Brillouin light scattering and microwave spectroscopy techniques. It is found that the width modulated crystal does not manifest noticeable Bragg reflections, but still demonstrates a pronounced band gap in its transmission characteristic. The phenomenon can be explained by the destructive interference between different frequency-degenerated spin-wave modes excited by the crystal. Such a reflection-less crystal is promising for future design of multi-element magnonic devices.

近年来，由于其在微波频率下的信息处理中的潜在应用，对镁磁晶体等人造磁性介质的兴趣大大增加。这些晶体的主要特征是在自旋波谱中存在带隙，这通常是由于自旋波在人工创建的周期性结构上的布拉格反射所致。在这里，我们通过布里渊光散射和微波光谱技术研究了在纵向磁化的宽度和厚度调制的钇铁石榴石波导中的自旋波传播。已经发现，宽度调制的晶体没有表现出明显的布拉格反射，但是在其透射特性中仍然显示出明显的带隙。这种现象可以用晶体激发的不同频率退化的自旋波模式之间的相消干涉来解释。这样的无反射晶体有望用于未来的多元素磁器件的设计。