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Orbital current has attracted significant attention in recent years due to its potential for energy-efficient magnetization control without the need for materials with strong spin–orbit coupling. However, the fundamental mechanisms governing orbital transport remain elusive. In this study, we systematically explore orbital transport in Ti/Ni bilayers through orbital pumping, drawing an analogy to spin pumping. The orbital current is generated and injected into the Ti layer via the microwave-driven orbital dynamics in Ni, facilitated by its strong spin–orbit correlation. We employed thickness-dependent ferromagnetic resonance measurements and angular-dependent inverse orbital Hall effect (IOHE) detection to probe orbital transport in Ti based on the conventional spin-pumping methodology. The observed enhancement in the damping factor indicates an orbital-diffusion length of ∼5.3 ± 3.7 nm, while IOHE-based estimation suggests a value of around 4.0 ± 1.2 nm, which confirms its short orbital-diffusion length. Furthermore, oblique Hanle measurements in the longitudinal configuration reveal an orbital relaxation time of approximately 16 ps. Our results establish that orbital pumping, analogous to the conventional spin-pumping framework, can serve as a robust technique for elucidating orbital transport mechanisms, paving the way for the design of efficient spin-orbitronic devices. 

Multichannel coupling in hybrid systems makes an attractive testbed not only because of the distinct advantages entailed by each constituent mode but also because the opportunity to leverage interference among the various excitation pathways. Here, via combined analytical calculation and experiment, we demonstrate that the phase of the magnetization precession at the interface of a coupled yttrium iron garnet (YIG)/permalloy (Py) bilayer is collectively controlled by the microwave photon field torque and the interlayer exchange torque, manifesting a coherent, dual-channel excitation scheme that effectively tunes the magneto-optical spectrum. The different torque contributions vary with frequency, external bias field, and type of interlayer coupling between YIG and Py, which further results in destructive or constructive interferences between the two excitation channels, and hence selective suppression or amplification of the hybridized magnon modes. 

Improving the photon-magnon coupling strength can be done by tuning the structure of microwave resonators to better interact with the magnon counterpart. Planar resonators accommodating unconventional photon modes beyond the half- and quarter-wavelength designs have been explored due to their optimized mode profiles and potentials for on-chip integration. Here, we designed and fabricated an actively controlled ring resonator supporting the spoof localized surface plasmons (LSPs), and implemented it in the investigation of photon-magnon coupling for hybrid magnonic applications. We demonstrated gain-assisted photon-magnon coupling with the YIG magnon mode under several different sample geometries. The achieved coupling amplification largely benefits from the high quality factor (Q-factor) due to the additional gain provided by a semiconductor amplifier, which effectively increases the Q-factor from a nearly null state (passive resonance) to more than 1000 for a quadrupole LSP mode. Our results suggest an additional control knob for manipulating photon-magnon coupled systems exploiting external controls of gain and loss. 

Abstract The opto-electronic oscillators (OEOs) hosting self-sustained oscillations by a time-delayed mechanism are of particular interest in long-haul signal transmission and processing. On the other hand, owing to their unique tunability and compatibility, magnons—as elementary excitations of spin waves—are advantageous carriers for coherent signal transduction across different platforms. In this work, we integrated an opto-electronic oscillator with a magnonic oscillator consisting of a microwave waveguide and a yttrium iron garnet sphere. We find that, in the presence of the magnetic sphere, the oscillator power spectrum exhibits sidebands flanking the fundamental OEO modes. The measured waveguide transmission reveals anti-crossing gaps, a hallmark of the coupling between the opto-electronic oscillator modes and the Walker modes of the sphere. Experimental results are well reproduced by a coupled-mode theory that accounts for nonlinear magnetostrictive interactions mediated by the magnetic sphere. Leveraging the advanced fiber-optic technologies in opto-electronics, this work lays out a new, hybrid platform for investigating long-distance coupling and nonlinearity in coherent magnonic phenomena. 

Abstract This work is on the design, fabrication and characterization of a hexagonal ferrite band-pass filter that can be tuned either with a magnetic field or an electric field. The filter operation is based on a straight-edge Y-type hexagonal ferrite resonator symmetrically coupled to the input and output microstrip transmission lines. The Zn₂Yfilter demonstrated magnetic field tunability in the 8–12 GHz frequency range by applying an in-plane bias magnetic fieldH₀provided by a built-in permanent magnet. The insertion loss and 3 dB bandwidth within this band were 8.6 ± 0.4 dB and 350 ± 40 MHz, respectively. The electric fieldEtunability of the pass-band of the device was facilitated by the nonlinear magnetoelectric effect (NLME) in the ferrite. TheE-tuning of the center frequency of the filter by (1150 ± 90) MHz was obtained for an input DC electric power of 200 mW. With efforts directed at a significant reduction in the insertion loss, the compact and power efficient magnetic and electric field tunable Zn₂Y band-pass filter has the potential for use in novel reconfigurable RF/microwave devices and communication systems.