The cross-integration of spin-wave and superconducting technologies is a promising method for creating novel hybrid devices for future information processing technologies to store, manipulate, or convert data in both classical and quantum regimes. Hybrid magnon–polariton systems have been widely studied using bulk Yttrium Iron Garnet (Y3Fe5O12, YIG) and three-dimensional microwave photon cavities. However, limitations in YIG growth have, thus far, prevented its incorporation into CMOS compatible technologies, such as high-quality factor superconducting quantum technology. To overcome this impediment, we have used Plasma Focused Ion Beam (PFIB) technology—taking advantage of precision placement down to the micrometer scale—to integrate YIG with superconducting microwave devices. Ferromagnetic resonance has been measured at milliKelvin temperatures on PFIB-processed YIG samples using planar microwave circuits. Furthermore, we demonstrate strong coupling between superconducting resonators and YIG ferromagnetic resonance modes by maintaining reasonably low loss while reducing the system down to the micrometer scale. This achievement of strong coupling on-chip is a crucial step toward fabrication of functional hybrid quantum devices from spin-wave and superconducting components.

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Electromagnetic interference shielding composite materials can be designed with properties that are tailored for specific applications. We have explored the magnetic properties of Ni-coated carbon fibers embedded in a polymer matrix through an extrusion process. This method can produce large, pliable flat sheets, which can be easily bent and shaped. Microscopy imaging shows that the extrusion process preferentially orders most of the fibers with their long axis along the extrusion direction. The measured samples reached 90% of the saturation magnetization value at a field of approximately 800 Oe along the extrusion direction, much lower than needed for other directions (in-plane perpendicular to the extrusion or perpendicular to the foil surface). A field on the order of 6 kOe must be applied to obtain the full saturation of the magnetization in all three directions. The absorption characteristics were measured, with zero external applied field to determine the shielding effectiveness of the composite materials for multiple orientations with respect to the TE10 mode of an S-band waveguide. The nickel-coated carbon fiber composite materials exhibit dramatic orientation-dependent shielding effectiveness. The most effective orientation has shielding effectiveness of up to 45 dB at 4.5 GHz, which is comparable to multi-walled carbon nanotube composites with similar volumetric filling fractions.

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