arXiv subjects

Aurélien Manchon

Publications and source records attributed to Aurélien Manchon.

At least 19 recordsLinked to original sources

arXiv2026

Chiral Damping-Induced Chirality Switching and Control of Domain Walls in Antiferromagnets

We investigate the impact of chiral damping (CD) on current-driven domain-wall (DW) dynamics in antiferromagnets (AFMs). Asymmetric CD between sublattices generates off-diagonal components in the DW mass tensor, thereby coupling translational and rotational modes. When CD is modulated by an ac gate voltage via the Rashba spin-orbit interaction (RSOI), symmetric and asymmetric contributions induce oscillations in the DW velocity and tilt angle, respectively. A perturbative analysis yields explicit expressions for the oscillation amplitudes, in quantitative agreement with numerical simulations. Remarkably, even in the absence of Dzyaloshinskii-Moriya interaction (DMI), asymmetric CD enables chirality switching between Néel- and Bloch-type DWs. Finally, by exploiting the relativistic Lorentz contraction of the DW width at high driving currents, we propose an experimentally viable protocol to qualitatively and quantitatively extract the CD contribution. These results establish clear experimental signatures of CD in antiferromagnetic DW dynamics and demonstrate its potential as a control parameter for magnetic textures.

cond-mat.mes-hall↗

arXiv2026

Higher-order Hall response arises from octupole order and scalar spin chirality in a noncollinear antiferromagnet

Noncollinear antiferromagnets can generate a transverse electrical response known as the anomalous Hall effect, even though they possess almost no net magnetization. The microscopic origin of this behaviour, however, has remained unclear because conventional measurement geometries mix different contributions to the measured response. Here, we show that applying magnetic fields in selected in-plane directions allows us to disentangle the mechanisms underlying the Hall effect in a representative noncollinear antiferromagnet. By suppressing any dipole-related signal, we isolate a purely octupole-driven Hall response that exhibits a characteristic three-fold angular symmetry. At low magnetic fields, we further observe an additional Hall-like contribution that arises from the scalar spin chirality associated with noncoplanar spin textures. Combining symmetry analysis, first-principles calculations, and transport measurements, we reveal that octupole order, dipole moments, and chirality coexist and contribute in distinct field regimes. These findings establish a framework for identifying and controlling complex magnetic order parameters for spintronic applications.

cond-mat.mes-hall↗

arXiv2025

Colloquium: A critique on van der Waals and two-dimensional magnets

Magnetic two-dimensional (2D) crystals were isolated about a decade ago, triggering a tremendous research activity worldwide. This colloquium raises a stiff question: what is really new about them? At first sight, they seem to be purer implementations of 2D spin models than traditional systems such as ultra-thin films. Yet, they partly realized their promises so far, and whether they give fresh perspectives on long-standing predictions in statistical physics is still an open question. Undoubtedly, they are uniquely amenable to electric-field effect, susceptible to mechanical deformation, and sensitive to moirés, for example. They represent interesting platforms for exploring, challenging, or simply revisiting a wide range of phenomena in condensed matter magnetism. This colloquium intends to offer a critical, yet not necessarily skeptical, overview of the field, clarifying what we believe could be unique with 2D magnets, related quasi-2D van der Waals magnets, and their heterostructures.

cond-mat.mtrl-sci↗

arXiv2025

Multipolar orbital relaxation of the $t_{2g}$ states

Using a nonperturbative approach, the relaxation rate of orbital dipolar and quadrupolar moments is computed analytically for the t2g states. In the presence of short-range impurities and in the absence of spin-orbit coupling, the orbital relaxation emerges from the competition between momentum scattering and the effect of the crystal field. In the case of weak disorder, the orbital relaxation time is proportional to the momentum scattering time: each scattering event contributes to destroying the orbital moment. In the case of strong disorder, the effect of the crystal field is averaged out, and the orbital relaxation time is inversely proportional to the momentum scattering. We finally find that the dipolar and quadrupolar orbital moments are coupled by the crystal field, resulting in a complex dynamical behavior upon orbital injection.

cond-mat.mes-hall↗

arXiv2025

Coexistence of unconventional spin-orbit torque and in-plane Hall effect in a single ferromagnetic layer

The symmetry of a material fundamentally governs its spin transport properties. While unconventional spin transport phenomena have been predominantly explored in low-symmetry systems (e.g., $C_{1v}$ symmetry), high-symmetry crystals--which constitute the majority of industry-compatible materials--are generally expected to exhibit only conventional spin-transport behavior. Here, we report the coexistence of two unconventional spin transport effects, the crystal spin-orbit torque (CSOT) and the crystal in-plane Hall effect (CIHE), in a CoPt single ferromagnetic layer with $C_{3v}$ symmetry. Leveraging the CSOT, we achieve nearly 100% field-free perpendicular magnetization switching in a 6 nm CoPt layer at room temperature. Simultaneously, the CIHE observed in this material exhibits nearly identical dependencies on both current angle and growth temperature as the CSOT. Symmetry analysis confirms that both effects share a common physical origin. Our work not only establishes CoPt as a high-performance spin-orbit material, but also demonstrates that unconventional spin transport can be realized in high-symmetry systems, thereby opening a broad pathway for their application in practical spintronics.

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arXiv2025

Interaction-Induced Topological Phase Transition in Magnetic Weyl Semimetals

Despite the tremendous interest raised by the recent realization of magnetic Weyl semimetals and the observation of giant anomalous Hall signals, most of the theories used to interpret experimental data overlook the influence of magnetic fluctuations, which are ubiquitous in such materials and can massively impact topological and transport properties. In this work, we predict that in such magnetic topological systems, the interaction between electrons and magnons substantially destabilizes the Weyl nodes, leading to a topological phase transition below the Curie temperature. Remarkably, the sensitivity of the Weyl nodes to electron-magnon interaction depends on their spin chirality. We find that Weyl nodes with a trivial chirality are more sensitive to electron-magnon interactions than Weyl nodes presenting an inverted chirality, demonstrating the resilience of the latter compared to the former. Our results open perspectives for the interpretation of the transport signatures of Weyl semimetals, especially close to the Curie temperature.

cond-mat.mes-hall↗

arXiv2025

Efficient Generation of Spin Currents in Altermagnets via Magnon Drag

Altermagnets, a recently identified class of magnetic materials, possess a spin-split Fermi surface that results in the so-called spin splitter effect, enabling the generation of a spin current transverse to the injection direction and whose polarization lies along the Néel vector. In this study, we investigate how magnons interact with electrons in an altermagnetic metal. We find that while the electron-magnon interaction does not perturb the magnon dispersion, a charge current flowing in the material can induce a transverse magnon spin current, analogous to the electronic spin splitter effect. This spin current possesses both electronic and magnonic characteristics, i.e., a chemical potential dependence and a strong temperature dependence. This effect realizes the efficient generation of spin currents via magnons without depending on the material's spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2025

Giant Orbital Torque-driven Picosecond Switching in Magnetic Tunnel Junctions

Orbital Hall effect was recently discovered as a novel pathway for driving magnetic moment. However, the integration of orbital Hall effect in magnetic memories suffers from low orbital-to-spin conversion efficiency and incompatibility with magnetic tunnel junctions. Here we demonstrate an orbital Hall effect-driven magnetic tunnel junction based on Ru/W bilayer, where the Ru layer possesses a strong orbital Hall conductivity and the α-W layer features an orbital-to-spin conversion efficiency exceeding 90% because of the large orbit-spin diffusivity. By harnessing the giant orbital torque, we achieve a 28.7-picosecond switching and a five to eight-fold reduction in driving voltages over conventional spin-orbit torque magnetic memories. Our work bridges the critical gap between orbital effects and magnetic memory applications, significantly advancing the field of spintronics and orbitronics.

cond-mat.mtrl-sci↗

arXiv2024

Phenomenology of orbital torque, pumping and mixing conductance in metallic bilayers

The conversion between spin and orbital currents is at the origin of the orbital torque and its Onsager reciprocal, the orbital pumping. Here, we propose a phenomenological model to describe the orbital torque in magnetic bilayers composed of an orbital source (i.e., a light metal such as Ti, Ru, CuOx...) and a spin-orbit coupled magnet (i.e., typically Ni, (Co/Pt)$_n$, etc.). This approach accounts for spin-to-orbit and orbit-to-spin conversion in the ferromagnet and at the interface. We show that the orbital torque arises from a compromise between orbital current injection from the orbital source to the ferromagnet and spin current backflow from the ferromagnet back to the orbital source. We also discuss the concept of orbital-mixing conductance and introduce the "orbit-spin-" and "spin-orbit-mixing" conductances that govern the orbital torque and orbital pumping, respectively.

cond-mat.mes-hall↗

arXiv2024

Spin and Orbital Rashba effects at the Ni/HfO$_2$ interface

We predict the giant ferroelectric control of interfacial properties of Ni/HfO2, namely, (i) the magnetocrystalline anisotropy and (ii) the inverse spin and orbital Rashba effects. The reversible control of magnetic properties using electric gating is a promising route to low-energy consumption magnetic devices, including memories and logic gates. Synthetic multiferroics, composed of a ferroelectric in proximity to a magnet, stand out as a promising platform for such devices. Using a combination of $ab$ $initio$ simulations and transport calculations, we demonstrate that reversing the electric polarization modulates the interface magnetocrystalline anisotropy from in-plane to out-of-plane. This modulation compares favorably with recent reports obtained upon electromigration induced by ionic gating. In addition, we find that the current-driven spin and orbital densities at the interface can be modulated by about 50% and 30%, respectively. This giant modulation of the spin-charge and orbit-charge conversion efficiencies opens appealing avenues for voltage-controlled spin- and orbitronics devices.

cond-mat.mtrl-sci↗

arXiv2024

Adiabatic Spin and Orbital Pumping in Metallic Heterostructures

In this study, we investigate the spin and orbital densities induced by magnetization dynamics in a planar bilayer heterostructure. To do this, we employed a theory of adiabatic pumping using the Keldysh formalism and Wigner expansion. We first conduct simulations on a model system to determine the parameters that control the spin and orbital pumping into an adjacent non-magnetic metal. We conclude that, in principle, the orbital pumping can be as significant as spin pumping when the spin-orbit coupling is present in the ferromagnet. We extend the study to realistic heterostructures involving heavy metals (W, Pt, Au) and light metals (Ti, Cu) by using first-principles calculations. We demonstrate that orbital pumping is favored in metals with $d$ states close to the Fermi level, such as Ti, Pt, and W, but is quenched in materials lacking such states, such as Cu and Au. Orbital injection is also favored in materials with strong spin-orbit coupling, leading to large orbital pumping in Ni/(Pt, W) bilayers.

cond-mat.mes-hall↗

arXiv2024

Orbital Kerr effect and terahertz detection via the nonlinear Hall effect

We investigate the optical response induced by a d.c. current flowing in a nonmagnetic material that lacks inversion symmetry. In this class of materials, the flowing current experiences a nonlinear Hall effect and induces a nonequilibrium orbital magnetization, even in the absence of spin-orbit coupling. As a result, an orbital-driven Kerr effect arises that can be used to probe not only the orbital magnetization but also the nonlinear Hall effect. In addition, in the long wavelength limit, the nonlinear Hall effect leads to a rectification current that can be used to detect terahertz radiation. We apply the theory to selected model systems, such as WTe$_2$ bilayer and metallic superlattices. The nonequilibrium orbital Kerr efficiencies obtained in these systems are comparable to the largest values reported experimentally in GaAs and MoS$_2$, exceeding the values reported in metals and suggesting a large terahertz current responsivity.

cond-mat.mtrl-sci↗

arXiv2024

Giant Spin-Orbit Torque in Cr-based Janus Transition Metal Dichalcogenides

We report a very large spin-orbit torque (SOT) capability of chromium-based transition metal dichalcogenides (TMD) in their Janus forms CrXTe, with X=S,Se. The structural inversion symmetry breaking, inherent to Janus structures is responsible for a large SOT response generated by giant Rashba splitting, equivalent to that obtained by applying a transverse electric field of $\sim 100 \,\text{V} \,\text{nm}^{-1}$ in non-Janus CrTe\textsubscript{2}, completely out of experimental reach. By performing transport simulations on custom-made Wannier tight-binding models, Janus systems are found to exhibit a SOT performance comparable to the most efficient two-dimensional materials, while allowing for field-free perpendicular magnetization switching owing to their reduced in-plane symmetry. Altogether, our findings evidence that magnetic Janus TMDs stand as suitable candidates for ultimate SOT-MRAM devices.

cond-mat.mtrl-sci↗

arXiv2024

Orbital Pumping by Magnetization Dynamics in Ferromagnets

We show that dynamics of the magnetization in ferromagnets can pump the orbital angular momentum, which we denote by orbital pumping. This is the reciprocal phenomenon to the orbital torque that induces magnetization dynamics by the orbital angular momentum in non-equilibrium. The orbital pumping is analogous to the spin pumping established in spintronics but requires the spin-orbit coupling for the orbital angular momentum to interact with the magnetization. We develop a formalism that describes the generation of the orbital angular momentum by magnetization dynamics within the adiabatic perturbation theory. Based on this, we perform first-principles calculation of the orbital pumping in prototypical $3d$ ferromagnets, Fe, Co, and Ni. The results show that the ratio between the orbital pumping and the spin pumping ranges from 5 to 15 percents, being smallest in Fe and largest in Ni. This implies that ferromagnetic Ni is a good candidate for measuring the orbital pumping. Implications of our results on experiments are also discussed.

cond-mat.mes-hall↗

arXiv2024

Impact of Magnon Interactions on Transport in Honeycomb Antiferromagnets

The thermal transport of magnons has attracted substantial attention as an energy-efficient alternative to the transport of electrons. Most theoretical studies so far have been carried out within the frame of the linear spin-wave theory, which dramatically fails upon increasing the temperature and in the presence of competing interactions. In this work, we consider the impact of three- and four-magnon interactions in a honeycomb antiferromagnet, where such interactions are remarkably strong even at zero temperature. Using a combination of quantum field theory and mean-field theory, we compute the band structure of the interacting magnons and investigate the spin Nernst effect. We find that in the presence of in-plane Dzyaloshinskii-Moriya Interaction, the three-magnon interaction induces a non-reciprocal band splitting, even at zero temperature, leading to an enhancement of the spin Nernst conductivity. In contrast, the four-magnon interaction renormalizes the magnon spectrum at high temperatures, leading to a reduction of the overall magnon spin Nernst effect. These results suggest that interactions can massively influence the transport properties of magnons in antiferromagnets, even at zero temperature, and should be taken into account for predictive modeling.

cond-mat.mes-hall↗

arXiv2023

Non-relativistic torque and Edelstein effect in noncollinear magnets

The Edelstein effect is the origin of the spin-orbit torque: a current-induced torque that is used for the electrical control of ferromagnetic and antiferromagnetic materials. This effect originates from the relativistic spin-orbit coupling, which necessitates utilizing materials with heavy elements. Here we show that in magnetic materials with non-collinear magnetic order, the Edelstein effect and consequently also a current-induced torque can exist even in the absence of the spin-orbit coupling. Using group symmetry analysis, model calculations, and realistic simulations on selected compounds, we identify large classes of non-collinear magnet candidates and demonstrate that the current-driven torque is of similar magnitude as the celebrated spin-orbit torque in conventional transition metal structures. We also show that this torque can exist in an insulating material, which could allow for highly efficient electrical control of magnetic order.

cond-mat.mtrl-sci↗

arXiv2023

Topological Phases in Magnonics

Magnonics or magnon spintronics is an emerging field focusing on generating, detecting, and manipulating magnons. As charge-neutral quasi-particles, magnons are promising information carriers because of their low energy dissipation and long coherence length. In the past decade, topological phases in magnonics have attracted intensive attention due to their fundamental importance in condensed-matter physics and potential applications of spintronic devices. In this review, we mainly focus on recent progress in topological magnonics, such as the Hall effect of magnons, magnon Chern insulators, topological magnon semimetals, etc. In addition, the evidence supporting topological phases in magnonics and candidate materials are also discussed and summarized. The aim of this review is to provide readers with a comprehensive and systematic understanding of the recent developments in topological magnonics.

cond-mat.mes-hall↗

arXiv2023

Orbital Hall physics in two-dimensional Dirac materials

Orbitronics has recently emerged as a very active research topic after several proposals aiming to exploit the orbital degree of freedom for charge-free electronics. In this communication, we investigate orbital transport in selected two-dimensional systems to better understand which parameters govern the intra-atomic and inter-atomic contributions to the orbital Hall effect. We study the impact of the gap, the role of the materials' topology and the influence of the disorder on spin and orbital Hall transport. Starting from the Kane-Mele model, we describe how the orbital moment behaves depending on the material's topology and clarify the influence of the gap on the orbital Hall conductivity. We then extend the study to realistic topologically trivial and non-trivial materials, and find that the topology has little qualitative influence on the orbital Hall conductivity. In contrast, we observe that the energy dispersion has a more dramatic impact, especially in the presence of disorder. Remarkably, our results suggest that the intra-atomic orbital Hall current is more robust against scattering than the inter-atomic one, without further impact of the topological properties of the system under consideration.

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