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

Abstract

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.

Resonant Spin Transmission Mediated by Magnons in a Magnetic Insulator Multilayer Structure

“…This observed behavior indicates an antiferromagnetic interfacial exchange coupling between Py and YIG, which is consistent with previous reports on similar YIG/ ferromagnetic metal (FM) bilayer structures, including our own polarized neutron reflectometry study. [14,24,25] The magnon spin transmission in the multilayer structure is studied using the geometry shown in Figure 1e, where two electrodes are connected to the exposed regions of the bottom Pt layer on the opposite edges. The electrically connected sample is mounted onto a coplanar waveguide with its topside down for microwave excitation of magnetic resonance (see the Experimental Section).…”

“…This observed behavior indicates an antiferromagnetic interfacial exchange coupling between Py and YIG, which is consistent with previous reports on similar YIG/ferromagnetic metal (FM) bilayer structures, including our own polarized neutron reflectometry study. [ 14,24,25 ]…”

“…[4,5] Recently, employing magnetic and antiferromagnetic insulators as spacers in magnetic heterostructures, researchers have demonstrated that efficient spin transmission and conversion can be realized. [6][7][8][9][10][11][12][13][14][15][16][17] For example, it has been shown that by using a thin NiO layer as a spacer, the spin pumping signal generated from a ferromagnet can get on magnons can provide useful mechanisms for modulating spin current in future magnonic devices, similar to their electronic and photonic counterparts such as antireflection coatings and Fabry-Pérot cavities.…”

“…[ 4,5 ] Recently, employing magnetic and antiferromagnetic insulators as spacers in magnetic heterostructures, researchers have demonstrated that efficient spin transmission and conversion can be realized. [ 6–17 ] For example, it has been shown that by using a thin NiO layer as a spacer, the spin pumping signal generated from a ferromagnet can get enhanced under certain temperature due to the improved spin mixing conductance. [ 6,7 ] Besides, researchers have also shown that a NiO layer on top of topological insulator [ 16 ] or heavy metal [ 15,17 ] can allow transfer of spin current and result in magnetic switching through spin‐orbit torque.…”

Intrinsic Topological Magnons In Arrays of Magnetic Dipoles

“…Currents of spins can be produced by the transport of electrons or, without their aid, by the collective propagation of coupled precessing spins or spin waves 6 . In magnetically ordered systems, based on magnetic insulators, ferromagnetic metals or heterostructures, spin-wave excitations, and their quantized versions, magnons 7,8 can be controlled by varying the layer thicknesses and applying external fields [9][10][11][12] . In artificial magnonic crystals 13 , the periodic modulation of the magnetic properties can be engineered, which makes possible the formation of magnonic bands separated by gaps in one-dimensional, two-dimensional, and bicomponent structures 14 .…”