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Orbital torque and efficient magnetization switching using ultrathin Co|Al light-metal interfaces: Experiments and modeling
Authors:
N. Sebe,
A. Pezo,
S. Krishnia,
S. Collin,
J. -M. George,
A. Fert,
V. Cros,
H. Jaffrès
Abstract:
The emergence of the orbital degree of freedom in modern orbitronics offers a promising alternative to heavy metals for the efficient control of magnetization. In this context, identifying interfaces that exhibit orbital-momentum locking and an orbital Rashba-Edelstein response to an external electric field is of primary importance. In this work, we experimentally investigate the Co/Al system and…
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The emergence of the orbital degree of freedom in modern orbitronics offers a promising alternative to heavy metals for the efficient control of magnetization. In this context, identifying interfaces that exhibit orbital-momentum locking and an orbital Rashba-Edelstein response to an external electric field is of primary importance. In this work, we experimentally investigate the Co/Al system and extend the study to Co/Pt/Al structures. We show that inserting ultrathin Pt layers between Co and Al can significantly modify the orbital properties, highlighting the critical role of Co/Al orbital bonding in generating orbital polarization. We further model the orbital response of these systems using semi-phenomenological approaches and linear-response theory within the framework of density-functional theory.
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Submitted 20 December, 2025;
originally announced December 2025.
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Anatomy of torques from orbital Rashba textures: the case of Co/Al interfaces
Authors:
A. Pezo,
N. Sebe,
A. Manchon,
V. Cros,
H. Jaffrès
Abstract:
In the context of orbitronics, the rising of the orbital angular momentum generated at light metal interfaces from orbital textures via orbital Rashba-Edelstein effects nowadays represent extraordinary alternatives to the usual heavy-metal spin-based materials. In the light of very recent experimental results [\textcolor{blue}{S. Krishnia \textit{et al.}, Nanoletters 2023, 23, 6785}], starting fro…
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In the context of orbitronics, the rising of the orbital angular momentum generated at light metal interfaces from orbital textures via orbital Rashba-Edelstein effects nowadays represent extraordinary alternatives to the usual heavy-metal spin-based materials. In the light of very recent experimental results [\textcolor{blue}{S. Krishnia \textit{et al.}, Nanoletters 2023, 23, 6785}], starting from state-of-the-art density functional theory simulations, we provide theoretical insights into the emergence of very strong orbital torques at the Co/Al interface location a strong orbital Rashba texture. By using linear response theory, we calculate the exerted orbital torque amplitudes, mainly of field-like intraband character, acting onto the ultrathin Co. Moreover, we show that an insertion of a single atomic plane of Pt between Co and Al is enough to suppress the effect which questions about the anatomy of the torque action clearly behaving differently than in the standard way. This work opens new routes to the engineering of spintronic devices.
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Submitted 15 September, 2025; v1 submitted 20 March, 2025;
originally announced March 2025.
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Large Chiral Orbital Texture and Orbital Edelstein Effect in Co/Al Heterostructure
Authors:
Sergey A. Nikolaev,
Mairbek Chshiev,
Fatima Ibrahim,
Sachin Krishnia,
Nicolas Sebe,
Jean-Marie George,
Vincent Cros,
Henri Jaffrès,
Albert Fert
Abstract:
Recent experiments by S. Krishnia et al., Nano Lett. 23, 6785 (2023) reported an unprecedentedly large enhancement of torques upon inserting thin Al layer in Co/Pt heterostructure that suggested the presence of a Rashba-like interaction at the metallic Co/Al interface. Based on first-principles calculations, we reveal the emergence of a large helical orbital texture in reciprocal space at the inte…
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Recent experiments by S. Krishnia et al., Nano Lett. 23, 6785 (2023) reported an unprecedentedly large enhancement of torques upon inserting thin Al layer in Co/Pt heterostructure that suggested the presence of a Rashba-like interaction at the metallic Co/Al interface. Based on first-principles calculations, we reveal the emergence of a large helical orbital texture in reciprocal space at the interfacial Co layer, whose origin is attributed to the orbital Rashba effect due to the formation of the surface states at the Co/Al interface and where spin-orbit coupling is found to produce smaller contributions with a higher-order winding of the orbital momentum. Our results unveil that the orbital texture gives rise to a non-equilibrium orbital accumulation producing large current-induced torques, thus providing an essential theoretical background for the experimental data and advancing the use of orbital transport phenomena in all-metallic magnetic systems with light elements.
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Submitted 13 October, 2024;
originally announced October 2024.
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Interfacial spin-orbitronic effects controlled with different oxidation levels at the Co|Al interface
Authors:
Sachin Krishnia,
Libor Vojáček,
Tristan Da Câmara Santa Clara Gomes,
Nicolas Sebe,
Fatima Ibrahim,
Jing Li,
Luis Moreno Vicente-Arche,
Sophie Collin,
Thibaud Denneulin,
Rafal E. Dunin-Borkowski,
Philippe Ohresser,
Nicolas Jaouen,
André Thiaville,
Albert Fert,
Henri Jaffrès,
Mairbek Chshiev,
Nicolas Reyren,
Vincent Cros
Abstract:
Perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions are key interactions in modern spintronics. These interactions are thought to be dominated by the oxidation of the Co|Al interface in the archetypal Platinum-Cobalt-Aluminum oxide system. Here, we observe a double sign change in the anisotropy and about threefold variation in interfacial chiral interaction, influenced n…
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Perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions are key interactions in modern spintronics. These interactions are thought to be dominated by the oxidation of the Co|Al interface in the archetypal Platinum-Cobalt-Aluminum oxide system. Here, we observe a double sign change in the anisotropy and about threefold variation in interfacial chiral interaction, influenced not only by the oxidation, but also by the metallic Al thickness. Contrary to previous assumptions about negligible spin-orbit effects at light metal interfaces, we not only observe strong PMA with fully oxidized Al, decreasing and turning negative (in-plane) with less oxygen at the Co|Al interface, we also observe that the magnetic anisotropy reverts to positive (out-of-plane) values at fully metallic Co|Al interface. These findings suggest modification in Co d band via Co|Al orbital hybridization, an effect supported by X-ray absorption spectroscopy and ab initio theory calculations, highlighting the key impact of strain on interfacial mechanisms at fully metallic Co|Al interface.
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Submitted 16 September, 2024;
originally announced September 2024.
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Spin-orbit readout using thin films of topological insulator Sb2Te3 deposited by industrial magnetron sputtering
Authors:
S. Teresi,
N. Sebe,
T. Frottier,
J. Patterson,
A. Kandazoglou,
P. Noël,
P. Sgarro,
D. Térébénec,
N. Bernier,
F. Hippert,
J. -P. Attané,
L. Vila,
P. Noé,
M. Cosset-Chéneau
Abstract:
Driving a spin-logic circuit requires the production of a large output signal by spin-charge interconversion in spin-orbit readout devices. This should be possible by using topological insulators, which are known for their high spin-charge interconversion efficiency. However, high-quality topological insulators have so far only been obtained on a small scale, or with large scale deposition techniq…
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Driving a spin-logic circuit requires the production of a large output signal by spin-charge interconversion in spin-orbit readout devices. This should be possible by using topological insulators, which are known for their high spin-charge interconversion efficiency. However, high-quality topological insulators have so far only been obtained on a small scale, or with large scale deposition techniques which are not compatible with conventional industrial deposition processes. The nanopatterning and electrical spin injection into these materials has also proven difficult due to their fragile structure and low spin conductance. We present the fabrication of a spin-orbit readout device from the topological insulator Sb2Te3 deposited by large-scale industrial magnetron sputtering on SiO2. Despite a modification of the Sb2Te3 layer structural properties during the device nanofabrication, we measured a sizeable output voltage that can be unambiguously ascribed to a spin-charge interconversion process.
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Submitted 23 June, 2023; v1 submitted 18 April, 2023;
originally announced April 2023.
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Experimental Observation of Curved Light-Cones in a Quantum Field Simulator
Authors:
Mohammadamin Tajik,
Marek Gluza,
Nicolas Sebe,
Philipp Schüttelkopf,
Federica Cataldini,
João Sabino,
Frederik Møller,
Si-Cong Ji,
Sebastian Erne,
Giacomo Guarnieri,
Spyros Sotiriadis,
Jens Eisert,
Jörg Schmiedmayer
Abstract:
We investigate signal propagation in a quantum field simulator of the Klein-Gordon model realized by two strongly coupled parallel one-dimensional quasi-condensates. By measuring local phononic fields after a quench, we observe the propagation of correlations along sharp light-cone fronts. If the local atomic density is inhomogeneous, these propagation fronts are curved. For sharp edges, the propa…
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We investigate signal propagation in a quantum field simulator of the Klein-Gordon model realized by two strongly coupled parallel one-dimensional quasi-condensates. By measuring local phononic fields after a quench, we observe the propagation of correlations along sharp light-cone fronts. If the local atomic density is inhomogeneous, these propagation fronts are curved. For sharp edges, the propagation fronts are reflected at the system's boundaries. By extracting the space-dependent variation of the front velocity from the data, we find agreement with theoretical predictions based on curved geodesics of an inhomogeneous metric. This work extends the range of quantum simulations of non-equilibrium field dynamics in general spacetime metrics.
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Submitted 19 September, 2022;
originally announced September 2022.