Manipulation of Coupling and Magnon Transport in Magnetic Metal-Insulator Hybrid Structures.

Ferromagnetic metals and insulators are widely used for generation, control, and detection of magnon spin signals. Most magnonic structures are based primarily on either magnetic insulators or ferromagnetic metals, while heterostructures integrating both of them are less explored. Here, by introducing a Pt/yttrium iron garnet (YIG)/permalloy (Py) hybrid structure grown on a Si substrate, we study the magnetic coupling and magnon transmission across the interface of the two magnetic layers. We find that within this structure, Py and YIG exhibit an antiferromagnetic coupling field as strong as 150 mT, as evidenced by both magnetometry and polarized neutron reflectometry measurements. By controlling individual layer thicknesses and external fields, we realize parallel and antiparallel magnetization configurations, which are further utilized to control the magnon current transmission. We show that a magnon spin valve with an on:off ratio of approximately 130% can be realized out of this multilayer structure at room temperature through both spin pumping and spin-Seebeck-effect experiments. Owing to the efficient control of magnon current and the compatibility with Si technology, the Pt/YIG/Py hybrid structure could potentially find applications in magnon-based logic and memory devices.