Strong on-Chip Microwave Photon-Magnon Coupling Using Ultralow-Damping Epitaxial Y3Fe5O12 Films at 2 K.

Y3Fe5O12 is arguably the best magnetic material for magnonic quantum information science (QIS) because of its extremely low damping. We report ultralow damping at 2 K in epitaxial Y3Fe5O12 thin films grown on a diamagnetic Y3Sc2Ga3O12 substrate that contains no rare-earth elements. Using these ultralow damping YIG films, we demonstrate for the first time strong coupling between magnons in patterned YIG thin films and microwave photons in a superconducting Nb resonator. This result paves the road toward scalable hybrid quantum systems that integrate superconducting microwave resonators, YIG film magnon conduits, and superconducting qubits into on-chip QIS devices.

Enhancing Perpendicular Magnetic Anisotropy in Garnet Ferrimagnet by Interfacing with Few-Layer WTe2.

Engineering magnetic anisotropy in a ferro- or ferrimagnetic (FM) thin film is crucial in a spintronic device. One way to modify the magnetic anisotropy is through the surface of the FM thin film. Here, we report the emergence of a perpendicular magnetic anisotropy (PMA) induced by interfacial interactions in a heterostructure comprised of a garnet ferrimagnet, Y3Fe5O12 (YIG), and a low-symmetry, high spin-orbit coupling (SOC) transition metal dichalcogenide, WTe2. At the same time, we also observed an enhancement in Gilbert damping in the WTe2-covered YIG area. Both the magnitude of interface-induced PMA and the Gilbert damping enhancement have no observable WTe2 thickness dependence down to a single quadruple layer, indicating that the interfacial interaction plays a critical role. The ability of WTe2 to enhance the PMA in FM thin film, combined with its previously reported capability to generate out-of-plane damping like spin torque, makes it desirable for magnetic memory applications.

Investigation of the Role of Rare-Earth Elements in Spin-Hall Topological Hall Effect in Pt/Ferrimagnetic-Garnet Bilayers.

Topological magnetic textures such as skyrmions are being extensively studied for their potential application in spintronic devices. Recently, low-damping ferrimagnetic insulators (FMI) such as Tm3Fe5O12 have attracted significant interest as potential candidates for hosting skyrmions. Here, we report the detection of the spin-Hall topological Hall effect (SH-THE) in Pt/Tm3Fe5O12 and Pt/Y3Fe5O12 bilayers grown on various orientations of Gd3Ga5O12 substrates as well as on epitaxial buffer layers of Y3Sc2Al3O12, which separates the FMI from the substrate without sacrificing the crystal quality. The presence of SH-THE in all of the bilayers and trilayers provides evidence that rare-earth ions in either the FMI or substrate may not be critical for inducing an interfacial Dzyaloshinskii-Moriya interaction that is necessary to stabilize magnetic textures. Additionally, the use of substrates with various crystal orientations alters the magnetic anisotropy, which shifts the temperatures and strength of the SH-THE.

Probing the Source of the Interfacial Dzyaloshinskii-Moriya Interaction Responsible for the Topological Hall Effect in Metal/Tm_{3}Fe_{5}O_{12} Systems.

The interfacial Dzyaloshinskii-Moriya interaction (DMI) is responsible for the emergence of topological spin textures such as skyrmions in layered structures based on metallic and insulating ferromagnetic films. However, there is active debate on where the interfacial DMI resides in magnetic insulator systems. We investigate the topological Hall effect, which is an indication of spin textures, in Tm_{3}Fe_{5}O_{12} films capped with various metals. The results reveal that Pt, W, and Au induce strong interfacial DMI and topological Hall effect, while Ta and Ti cannot. This study also provides insights into the mechanism of electrical detection of spin textures in magnetic insulator heterostructures.

Interfacial Rashba-Effect-Induced Anisotropy in Nonmagnetic-Material-Ferrimagnetic-Insulator Bilayers.

Interfacial magnetic anisotropy in magnetic insulators has been largely unexplored. Recently, interface-induced skyrmions and electrical control of magnetization have been discovered in insulator-based heterostructures, which demand a thorough understanding of interfacial interactions in these materials. We observe a substantial, tunable interfacial magnetic anisotropy between Tm_{3}Fe_{5}O_{12} epitaxial thin films and fifteen nonmagnetic materials spanning a significant portion of the periodic table, which we attribute to Rashba spin-orbit coupling. Our results show a clear distinction between nonmagnetic capping layers from the d block and the p block. This work offers a new path for controlling magnetic phases in magnetic insulators for low-loss spintronic applications.