Hanchen Wang

Last Name

Wang

First Name

Hanchen

ORCID

0000-0001-5646-0493

Organisational unit

03986 - Gambardella, Pietro / Gambardella, Pietro

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Publications 1 - 10 of 24

Deterministic switching of antiferromagnetic spin textures by nonlinear magnons
Chen, Jilei; Xu, Mingran; Wang, Jinlong; et al. (2025)
Nature Communications
Antiferromagnetic spin textures, compared to their ferromagnetic counterparts, innately possess high stability with respect to external disturbance and high-frequency dynamics compatible with ultrafast information processing. However, deterministic creation and reconfigurable switching of different antiferromagnetic spin textures have not been realized. Here, we demonstrate room-temperature deterministic switching between three antiferromagnetic textures identified by characteristically different high frequency dynamics in single-crystal hematite (α-Fe2O3). All three states are found to be remarkably stable and fully controllable, as confirmed by 1000 switching cycles and spatially resolved spectroscopy and they may be created by local magnetization switching in the nonlinear excitation regime. The switching to the following stable state requires only one microwave pulse (100 ns) with ultralow energy consumption (1 nJ). Our Brillouin light scattering (BLS) microscopy data reinforces that the detected magnon modes are associated to excitations of domain walls and circular spin textures. The progressive switching between the three distinct states imitates the weighted sum operation in neuromorphic computing, suggesting the possibility of using spin textures in antiferromagnets for information processing.
Current-Controlled Magnon-Magnon Coupling in an On-Chip Cavity Resonator
Wang, Hanchen; Legrand, William; Schlitz, Richard; et al. (2025)
Nano Letters
Harnessing spin currents to control magnon dynamics enables new functionalities in magnonic devices. Here, we demonstrate current-controlled magnon-magnon coupling between cavity and boundary modes in an ultrathin film of Bi-doped yttrium iron garnet (BiYIG). Cavity modes emerge in a BiYIG region between two Pt nanostripes, where interfacial anisotropy modifies the magnon dispersion. These modes hybridize with boundary magnons confined within the Pt-capped BiYIG, resulting in an anticrossing gap. Modeling based on dipole-exchange spin-wave dispersion accurately reproduces the observed modes and their hybridization. Spin current injection via the spin Hall effect in a Pt nanostripe disrupts the cavity boundary conditions and suppresses both cavity modes and hybridization upon driving the system beyond the damping compensation threshold. Furthermore, tuning the microwave power applied to a microstrip antenna enables controlled detuning of the anticrossing gap. Our findings provide a platform for exploring spin current-magnon interactions and designing on-chip reconfigurable magnonic devices.
Implementation of field-differential phase-resolved microwave magnetic spectroscopy
Legrand, William; Petrosyan, Davit; Wang, Hanchen; et al. (2025)
Review of Scientific Instruments
Microwave spectroscopies are central to the investigation of magnetic systems by enabling the identification of dynamical resonance modes and by providing quantitative information on key magnetic parameters. Experiments on magnetization dynamics based on inductive microwave techniques usually rely on either field-modulated power detection or phase-resolved detection using a vector network analyzer. While these two approaches bring separate advantages, they have rarely been combined together. In this work, we develop customized microwave instrumentation combining phase-resolved detection and magnetic field modulation to perform microwave spectroscopy of magnetic systems. We apply this technique to ferromagnetic resonance (FMR), where it enables a quantitative measurement of the magnetic susceptibility in systems with small volume and magnetization. This method of field-differential phase-resolved microwave magnetic spectroscopy is compared with other approaches and is shown to greatly improve the resolution of finely separated FMR peaks and the detection of small signals. Furthermore, we model and characterize comprehensively the inductive coupling of the magnetic system to the microwave circuit, which enables a quantitative analysis of the resonance peaks and the rejection of potential errors originating from too strong permeability, imperfect impedance matching, broadening induced by field inhomogeneity, and varying sample placement.
Long-range propagation of magnon polaritons in a canted antiferromagnet
Wang, Hanchen; Wang, Jinlong; Yu, Kanglin; et al. (2025)
Physical Review Applied
We report strong coupling between magnons and cavity photons in a single-crystalline slab of alpha-Fe2O3 (hematite) with canted antiferromagnetic order at room temperature. The hybridized magnon polaritons propagate over many millimeters due to their high group velocities, as experimentally characterized using time-of-flight spectroscopy. The conventional dipolar and spin-orbit-interaction-induced chirality can explain an observed nonreciprocity. Our findings highlight the potential of antiferromagnetic magnon polaritons for on-chip spin-based information technologies.
Observation of Coherent Gapless Magnons in an Antiferromagnet
Chen, Jilei; Jin, Zhejunyu; Yuan, Rundong; et al. (2025)
Physical Review Letters
Antiferromagnetic magnons possess high speed and are immune to external disturbance, making them promising for future magnonic circuits. In this Letter, we report the observation of gapless magnons in an easy-Axis antiferromagnet α-Fe2O3 at low temperatures. These antiferromagnetic magnons are detected at nearly zero frequency by all-electrical spin-wave spectroscopy and propagate along antiferromagnetic domain walls as revealed by our theoretical model and simulations. Moreover, we demonstrate high coherency of these gapless magnons by showing their strong coupling with microwave photons. Our results open the pathway for antiferromagnetic texture based magnonic devices operating at microwave frequencies.
Lattice-tunable Substituted Iron Garnets for Low-temperature Magnonics
Legrand, William; Kemna, Yana; Schären, Stefan; et al. (2025)
Advanced Functional Materials
The synthesis of nm-thick epitaxial films of iron garnets by physical vapor deposition has opened up exciting opportunities for the on-chip generation and processing of microwave signals encoded in magnons. However, iron garnet thin films suffer from demanding lattice-matching and stoichiometry requirements. Here a new approach to their synthesis is developed, enabling a precise and continuous tuning of iron garnet compositions based on the co-sputtering of binary oxides. By substituting a controlled proportion of iron with additional yttrium, Y3(YxFe5–x)O12 films of high crystalline quality are obtained, combining a widely tunable lattice parameter and excellent magnetization dynamics. This enables iron garnet thin films suited for cryogenic applications, which have long remained impractical due to microwave losses caused by paramagnetic garnet substrates. Low-temperature ferromagnetic resonance confirms the elimination of substrate paramagnetic losses for Y3(YxFe5–x)O12 films lattice-matched to Y3Sc2Ga3O12 (YSGG), a diamagnetic substrate. The Y3(YxFe5–x)O12 system can be matched to other substrates such as (Gd, Y)3Sc2Ga3O12. Bi-substituted films of (Bi0.8Y2.2)Fe5O12 also have ideal lattice matching to YSGG, demonstrating the versatility of this approach. This opens unprecedented options for cation substitutions in iron garnet films, offering a promising avenue to new properties and quantum magnonic devices operating in low-temperature environments.
Large interfacial Dzyaloshinskii–Moriya interaction of epitaxial perovskite La0.7Sr0.3MnO3 films
Yang, Liu; Zhang, Xiaotong; Wang, Hanchen; et al. (2025)
Applied Physics Reviews
The Dzyaloshinskii–Moriya interaction (DMI) is pivotal in stabilizing topological spin textures, a critical aspect of the rapidly advancing field of oxide-based spintronics. While skyrmions and the topological Hall effect have been widely studied in oxide films, experimental verification of interfacial DMI and its underlying mechanisms in oxide interfaces has remained largely unexplored. In this study, we report a significantly large interfacial DMI in La0.7Sr0.3MnO3 (LSMO) films grown on NdGaO3 substrates, with a DMI coefficient of 1.96 pJ/m—one to two orders of magnitude higher than previously observed in oxide systems. Our experiments, coupled with first-principles calculations, reveal that enhanced spin–orbit coupling at the LSMO/NdGaO3 interface, driven by a synergy between the 6s electrons of Nd and the 4f electrons, is the key to this large DMI. This breakthrough opens new avenues for controlling chiral spintronics in oxide-based materials, laying the groundwork for next-generation spintronic and magnonic devices.
Orbital Pumping in Ferrimagnetic Insulators
Wang, Hanchen; Kang, Min-Gu; Petrosyan, Davit; et al. (2025)
Physical Review Letters
We report the detection of pure orbital currents generated by both coherent and thermal magnons in the magnetic insulator Bi-doped yttrium iron garnet (BiYIG). The pumping of orbital and spin currents is jointly investigated in nanodevices made of naturally oxidized Cu, pure Cu, Pt, and Cr. The absence of charge conduction in BiYIG and the negligible spin-to-charge conversion of oxidized Cu allows us to disambiguate the orbital current contribution. Comparative measurements on YIG and BiYIG show that the origin of the orbital pumping in BiYIG/oxidized Cu is the dynamics of the orbital magnetization in the magnetic insulator. In Cr, the pumping signal is dominated by the negative spin Hall effect rather than the positive orbital Hall effect, indicating that orbital currents represent a minority of the total angular momentum current pumped from the magnetic insulator. Our results also evidence that improving the interfacial transparency significantly enhances pumping efficiencies, not only for spin but also for orbital currents.
Control of spin currents by magnon interference in a canted antiferromagnet
Sheng, Lutong; Duvakina, Anna; Wang, Hanchen; et al. (2025)
Nature Physics
Controlling the spin current lies at the heart of spintronics and its applications. In ferromagnets, the sign of spin currents is fixed once the current direction is determined. However, spin currents in antiferromagnets can possess opposite polarizations, but this requires enormous magnetic fields to lift the degeneracy between the two modes. Therefore, controlling spin currents with opposite polarization is still a challenge. Here we demonstrate the control of spin currents at room temperature by magnon interference in a canted antiferromagnet, namely, haematite that has recently been classified as an altermagnet. Magneto-optical characterization by Brillouin light scattering reveals that the spatial periodicity of the beating patterns is tunable via the microwave frequency. We further observe that the inverse spin Hall voltage changes sign as the frequency is tuned, evincing a frequency-controlled switching of polarization of pure spin currents. Our work highlights the use of antiferromagnetic magnon interference to control spin currents, which substantially extends the horizon for the emerging field of coherent antiferromagnetic spintronics.
Reconfigurable nonreciprocal excitation of propagating exchange spin waves in perpendicularly magnetized yttrium iron garnet thin films
Wang, Hanchen; Wang, Jinlong; Chen, Shuyao; et al. (2023)
Physical Review B
We report the nonreciprocal excitation of propagating forward volume exchange spin waves in yttrium iron garnet (YIG) thin film with perpendicular anisotropy by bringing the in-plane magnetization of Co20Fe60B20 (CoFeB) nanowires to resonance. All-electric spin-wave spectroscopy is used to measure propagating spin waves in YIG subjected to out-of-plane external magnetic fields. The nonreciprocity can be reconfigured by inverting the in-plane magnetization of the CoFeB nanowires. The exchange spin waves achieved in the experiments have wavelengths down to about 150 nm and fast group velocities of up to 1.6 km/s, which can be accounted for with the dipole-exchange spin-wave dispersion of the forward volume mode. Micromagnetic simulations reproduce these experimental features, verifying that the key physics behind this nonreciprocity is the intrinsically chiral dynamic stray fields generated by the resonating CoFeB magnetization. Our results provide key insights into advanced and high-frequency magnonic devices.

Publications 1 - 10 of 24

Hanchen Wang

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