Department of Electrical and Computer Engineering and National University of Singapore Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576, Singapore.
National Institute for Materials Science, Tsukuba 305-0047, Japan.
Sci Adv. 2016 Jul 1;2(7):e1501892. doi: 10.1126/sciadv.1501892. eCollection 2016 Jul.
Spin waves are propagating disturbances in the magnetization of magnetic materials. One of their interesting properties is nonreciprocity, exhibiting that their amplitude depends on the magnetization direction. Nonreciprocity in spin waves is of great interest in both fundamental science and applications because it offers an extra knob to control the flow of waves for the technological fields of logics and switch applications. We show a high nonreciprocity in spin waves from Ta/Py bilayer systems with out-of-plane magnetic fields. The nonreciprocity depends on the thickness of Ta underlayer, which is found to induce an interfacial anisotropy. The origin of observed high nonreciprocity is twofold: different polarities of the in-plane magnetization due to different angles of canted out-of-plane anisotropy and the spin pumping effect at the Ta/Py interface. Our findings provide an opportunity to engineer highly efficient, nonreciprocal spin wave-based applications, such as nonreciprocal microwave devices, magnonic logic gates, and information transports.
自旋波是磁性材料中磁化的传播扰动。它们的一个有趣特性是非互易性，表现为其幅度取决于磁化方向。自旋波的非互易性在基础科学和应用中都很有意义，因为它为逻辑和开关应用等技术领域的波的流动提供了额外的控制旋钮。我们在具有面外磁场的 Ta/Py 双层系统中展示了自旋波的高非互易性。非互易性取决于下 Ta 层的厚度，发现它会引起界面各向异性。观察到的高非互易性有两个原因：由于倾斜的面外各向异性的角度不同，导致面内磁化的不同极性，以及 Ta/Py 界面处的自旋泵浦效应。我们的发现为工程高效、非互易的基于自旋波的应用提供了机会，例如非互易微波器件、磁性逻辑门和信息传输。
