Manipulation of magnetic coupling and magnon transport in magnetic insulator-ferromagnetic metal hybrid structures

Magnetic insulators and ferromagnetic metals are widely used in spintronic structures for the generation of magnon spin current, control of magnetization states, and for detecting magnon spins. Most of the previous spintronic structures are based primarily on either magnetic insulators or ferromagnetic metals, and the heterostructures that integrate both have not been fully explored while they may exhibit new magnetic coupling and magnon transport properties. Here, we introduce a Pt/yttrium iron garnet (YIG)/permalloy(Py) hybrid structure grown on Si substrate, where YIG is a ferrimagnetic insulator and Py is a ferromagnetic metal. Surprisingly, the YIG and the Py layers show antiferromagnetic coupling when external field is small, and the two layers align to the same direction only when in-pane field is large enough, as evidenced by both vibrating-sample magnetometry and polarized neutron reflectometry measurements. More importantly, the parallel and antiparallel magnetization configurations in this YIG/Py structure could be utilized to control magnon spin current in spin-pumping and spin Seebeck experiments. With easy access to grow by magnetron sputtering, fully controllable magnetization configuration, and efficient control of magnon spin current, the Pt/YIG/Py hybrid structure could potentially find applications in spin logic devices that are fabricated on a Si chip.