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3D tomographic imaging of skyrmionic cocoons using HERALDO
Authors:
Jhon J. Chiliquinga-Jacome,
Matthieu Grelier,
Riccardo Battistelli,
William Bouckaert,
Krishnanjana Puzhekadavil Joy,
Sophie Collin,
Florian Godel,
Marisel Di Pietro Martínez,
Claire Donnelly,
Felix Büttner,
Horia Popescu,
Vincent Cros,
Nicolas Reyren,
Nicolas Jaouen
Abstract:
Uncovering the rich and intricate characteristics of three-dimensional (3D) magnetic textures is essential for functional materials such as magnetic multilayers, where the delicate balance of various magnetic interactions leads to complex 3D spin arrangements. Among these textures, skyrmionic cocoons-tubular 3D magnetic structures characterized by a closed magnetization surface wrapping around a c…
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Uncovering the rich and intricate characteristics of three-dimensional (3D) magnetic textures is essential for functional materials such as magnetic multilayers, where the delicate balance of various magnetic interactions leads to complex 3D spin arrangements. Among these textures, skyrmionic cocoons-tubular 3D magnetic structures characterized by a closed magnetization surface wrapping around a core-have emerged as particularly intriguing. Stabilized by competing magnetic interactions, these textures reside within a fraction of the thickness of the magnetic material and exhibit a typical lateral size of approximately 100 nm. Here, we present a vector tomographic reconstruction of the 3D magnetization in aperiodic Pt/Co/Al chiral multilayers, where skyrmionic cocoons have been recently reported. Using soft X-ray Holography with Extended Reference by Autocorrelation Linear Differential Operator (HERALDO), we acquire tomographic projections of the magnetic configuration and reconstruct the full 3D magnetization vector field with a spatial resolution of approximately 30 nm, as determined by Fourier shell correlation (FSC). This resolution allows us to observe critical features of the cocoons, such as their vertical misalignment and their overall chirality. Our findings demonstrate that HERALDO-based vector tomography is a powerful approach for revealing the internal structure and vertical extent of these nanoscale magnetic textures, offering new experimental insights into their intrinsic behavior.
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Submitted 21 January, 2026;
originally announced January 2026.
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Phonon-tunable THz magnonic emission in multiferroic heterostructures
Authors:
Sylvain Massabeau,
Amr Abdelsamie,
Florian Godel,
Filip Miljevic,
Noela Rezi,
Pascale Gemeiner,
Karim Bouzehouane,
Thomas Buttiens,
Sukhdeep Dhillon,
Thomas Maroutian,
Jean-Marie George,
Henri Jaffres,
Brahim Dkhil,
Stephane Fusil,
Vincent Garcia,
Romain Lebrun
Abstract:
Collective excitations such as magnons and polar phonons provide natural access to the terahertz (THz) regime, but efficient generation and tunability remain elusive. Multiferroic BiFeO3 combines both orders at room temperature, offering a unique platform for narrowband THz emission. Here, we achieve efficient sub-bandgap optical rectification of coupled phonon-polaritons near 2 THz in bare epitax…
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Collective excitations such as magnons and polar phonons provide natural access to the terahertz (THz) regime, but efficient generation and tunability remain elusive. Multiferroic BiFeO3 combines both orders at room temperature, offering a unique platform for narrowband THz emission. Here, we achieve efficient sub-bandgap optical rectification of coupled phonon-polaritons near 2 THz in bare epitaxial thin films. In Pt/BiFeO3 bilayers, we demonstrate that coupling the electromagnon branch with ultrafast strain waves, optically generated in Pt layers with various thicknesses, can produce tunable and narrowband emission between 0.4-0.8 THz. These results uncover the intertwined role of phonons, magnons, and magneto-acoustic dynamics in antiferromagnetic multiferroics, and establish these hybrid platforms as versatile engineered narrowband THz sources.
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Submitted 26 November, 2025;
originally announced November 2025.
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Straightforward Method to Orient Black Phosphorus from Bulk to Thin Layers using a Standard Green Laser
Authors:
Etienne Carré,
Frédéric Fossard,
Jean-Sébastien Mérot,
Denis Boivin,
Nicolas Horezan,
Victor Zatko,
Florian Godel,
Bruno Dlubak,
Marie-Blandine Martin,
Pierre Seneor,
Etienne Gaufres,
Julien Barjon,
Annick Loiseau,
Ingrid Stenger
Abstract:
The crystallographic orientation of anisotropic 2D materials plays a crucial role in their physical properties and device performance. However, standard orientation techniques such as transmission electron microscopy (TEM) or X-ray diffraction (XRD) can be complex and less accessible for routine characterization. In this study, we investigate the orientation of black phosphorus (BP) from bulk crys…
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The crystallographic orientation of anisotropic 2D materials plays a crucial role in their physical properties and device performance. However, standard orientation techniques such as transmission electron microscopy (TEM) or X-ray diffraction (XRD) can be complex and less accessible for routine characterization. In this study, we investigate the orientation of black phosphorus (BP) from bulk crystals to thin layers using angle-resolved polarized Raman spectroscopy (ARPRS) with a single-wavelength (514 nm) Raman setup. By incorporating thickness-dependent interference effects and anisotropic optical indices, this approach provides a reliable framework for orientation determination across different BP thicknesses. The method is validated through direct orientation measurements using TEM and Electron Backscattering Diffraction (EBSD), confirming its applicability to both thick and ultrathin samples. Given its simplicity and compatibility with widely available Raman setups, this approach offers a practical solution for characterizing BP orientation without requiring advanced structural characterization techniques.
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Submitted 6 August, 2025;
originally announced August 2025.
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Terahertz antiferromagnetic dynamics induced by ultrafast spin currents
Authors:
Sanjay René,
Artem Levchuk,
Amr Abdelsamie,
Zixin Li,
Pauline Dufour,
Arthur Chaudron,
Florian Godel,
Jean-Baptiste Moussy,
Karim Bouzehouane,
Stéphane Fusil,
Vincent Garcia,
Michel Viret,
Jean-Yves Chauleau
Abstract:
Insulating antiferromagnets are anticipated as the main protagonists of ultrafast spintronics, with their intrinsic terahertz dynamics and their abililty to transport spin information over long distances. However, direct transfer of spin angular momentum to an antiferromagnetic insulator at picosecond time scales remains to be demonstrated. Here, studying the ultrafast behaviour of ferromagnetic m…
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Insulating antiferromagnets are anticipated as the main protagonists of ultrafast spintronics, with their intrinsic terahertz dynamics and their abililty to transport spin information over long distances. However, direct transfer of spin angular momentum to an antiferromagnetic insulator at picosecond time scales remains to be demonstrated. Here, studying the ultrafast behaviour of ferromagnetic metal/antiferromagnetic insulator bilayers, we evidence the generation of coherent excitations in the antiferromagnet combined with a modulation of the demagnetization behavior of the ferromagnet. This confirms that magnetic information can indeed be propagated into antiferromagnetic spin waves at picosecond timescales, thereby opening an avenue towards ultrafast manipulation of magnetic information.
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Submitted 20 July, 2024;
originally announced July 2024.
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Control of the magnetic anisotropy in multi-repeat Pt/Co/Al heterostructures using magneto-ionic gating
Authors:
Tristan da Câmara Santa Clara Gomes,
Tanvi Bhatnagar-Schöffmann,
Sachin Krishnia,
Yanis Sassi,
Dedalo Sanz-Hernández,
Nicolas Reyren,
Marie-Blandine Martin,
Frederic Brunnett,
Sophie Collin,
Florian Godel,
Shimpei Ono,
Damien Querlioz,
Dafiné Ravelosona,
Vincent Cros,
Julie Grollier,
Pierre Seneor,
Liza Herrera Diez
Abstract:
Controlling magnetic properties through the application of an electric field is a significant challenge in modern nanomagnetism. In this study, we investigate the magneto-ionic control of magnetic anisotropy in the topmost Co layer in Ta/Pt/[Co/Al/Pt]$_n$/Co/Al/AlO$_\text{x}$ multilayer stacks comprising $n +1$ Co layers and its impact on the magnetic properties of the multilayers. We demonstrate…
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Controlling magnetic properties through the application of an electric field is a significant challenge in modern nanomagnetism. In this study, we investigate the magneto-ionic control of magnetic anisotropy in the topmost Co layer in Ta/Pt/[Co/Al/Pt]$_n$/Co/Al/AlO$_\text{x}$ multilayer stacks comprising $n +1$ Co layers and its impact on the magnetic properties of the multilayers. We demonstrate that the perpendicular magnetic anisotropy can be reversibly quenched through gate-driven oxidation of the intermediary Al layer between Co and AlO$_\text{x}$, enabling dynamic control of the magnetic layers contributing to the out-of-plane remanence - varying between $n$ and $n +1$. For multilayer configurations with $n = 2$ and $n = 4$, we observe reversible and non-volatile additions of 1/3 and 1/5, respectively, to the anomalous Hall effect amplitude based on the applied gate voltage. Magnetic imaging reveals that the gate-induced spin-reorientation transition occurs through the propagation of a single 90$^{\circ}$ magnetic domain wall separating the perpendicular and in-plane anisotropy states. In the 5-repetition multilayer, the modification leads to a doubling of the period of the magnetic domains at remanence. These results demonstrate that the magneto-ionic control of the anisotropy of a single magnetic layer can be used to control the magnetic properties of coupled multilayer systems, extending beyond the gating effects on a single magnetic layer.
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Submitted 23 July, 2024; v1 submitted 2 October, 2023;
originally announced October 2023.
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X-ray holography of skyrmionic cocoons in aperiodic magnetic multilayers
Authors:
M. Grelier,
R. Battistelli,
H. Popescu,
F. Godel,
A. Vecchiola,
S. Collin,
C. Léveillé,
K. Bouzehouane,
F. Büttner,
V. Cros,
N. Jaouen,
N. Reyren
Abstract:
The development and characterization of three-dimensional (3D) topological magnetic textures has become an important topic in modern magnetism both for fundamental and technological perspectives. Among the novel 3D spin textures, skyrmionic cocoons have been successfully stabilized in magnetic multilayers having a variable thickness of the ferromagnet in the vertical direction of the stack. These…
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The development and characterization of three-dimensional (3D) topological magnetic textures has become an important topic in modern magnetism both for fundamental and technological perspectives. Among the novel 3D spin textures, skyrmionic cocoons have been successfully stabilized in magnetic multilayers having a variable thickness of the ferromagnet in the vertical direction of the stack. These ellipsoidal 3D magnetic textures remain vertically confined in a fraction of the total thickness while coexisting with fully columnar skyrmions. Here, we use X-ray holography with about 15 nm lateral resolution to investigate how their properties depend on the field and temperature. We observe circular objects with different amplitude of contrast which evidences the presence of different 3D objects located in various vertical parts of the multilayer. Moreover, we witness during out-of-plane cycling an attractive interaction between cocoons located at various heights, mainly due to the stray field, which impacts their horizontal positioning. The X-ray holography measurements also allow to determine the size of the cocoons at remanence which, at room temperature, possess diameter close to 100 nm in average. Combining this transmission technique with magnetic force microscopy and micromagnetic simulations gives a precise insight into the 3D distribution of the magnetization which demonstrate the 3D nature of skyrmionic cocoons.
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Submitted 6 February, 2023;
originally announced February 2023.
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Compensation of anisotropy in spin-Hall devices for neuromorphic applications
Authors:
Pankaj Sethi,
Dédalo Sanz-Hernández,
Florian Godel,
Sachin Krishnia,
Fernando Ajejas,
Alice Mizrahi,
Vincent Cros,
Danijela Marković,
Julie Grollier
Abstract:
Spintronic nano-oscillators with reduced non-linearity could offer key benefits for realizing neuromorphic applications such as spike-based neurons and frequency multiplexing in neural networks. Here, we experimentally demonstrate the reduction in non-linearity of a spin-Hall nano-oscillator (SHNO) by compensation of its effective magnetic anisotropy. The study involves optimization of Co/Ni multi…
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Spintronic nano-oscillators with reduced non-linearity could offer key benefits for realizing neuromorphic applications such as spike-based neurons and frequency multiplexing in neural networks. Here, we experimentally demonstrate the reduction in non-linearity of a spin-Hall nano-oscillator (SHNO) by compensation of its effective magnetic anisotropy. The study involves optimization of Co/Ni multilayer growth to achieve the compensation, followed by spin diode measurements on patterned microstrips to quantify their anisotropy. The relation between the second ($H_{k2}$ = 0.47 mT) and the first order ($H_{k1}^{eff}$ = $-$0.8 mT) anisotropy fields reveals the existence of an easy cone, thereby validating the presence of compensation. Furthermore, we demonstrate a synapse based on the compensated spin diode which has a fixed frequency when the input power is varied. We then study the current-induced auto-oscillation properties of SHNOs on compensated films by patterning nano-constrictions of widths 200 and 100 nm. The invariance of the resonance frequency and linewidth of the compensated SHNO with applied dc current indicates the absence of non-linearity. This independence is maintained irrespective of the applied external fields and its orientations. The compensated SHNO obtained has a linewidth of 1.1 MHz and a peak output power of up to 1 pW/MHz emulating a nano-neuron with a low linewidth and a fixed frequency.
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Submitted 10 January, 2023;
originally announced January 2023.
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Three-dimensional skyrmionic cocoons in magnetic multilayers
Authors:
Matthieu Grelier,
Florian Godel,
Aymeric Vecchiola,
Sophie Collin,
Karim Bouzehouane,
Albert Fert,
Vincent Cros,
Nicolas Reyren
Abstract:
Three-dimensional (3D) topological spin textures emerge as promising quasi-particles for encoding information in future spintronic devices. The third dimension provides more malleability regarding their magnetic properties as well as more flexibility for potential applications. However, the stabilization and characterization of such quasi-particles in easily implementable systems remain a work in…
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Three-dimensional (3D) topological spin textures emerge as promising quasi-particles for encoding information in future spintronic devices. The third dimension provides more malleability regarding their magnetic properties as well as more flexibility for potential applications. However, the stabilization and characterization of such quasi-particles in easily implementable systems remain a work in progress. Here we observe a new type of 3D magnetic textures that we called skyrmionic cocoons that sits in the interior of magnetic thin films multilayers and possesses a characteristic ellipsoidal shape. Interestingly, these cocoons can coexist with more standard `tubular' skyrmions going through all the multilayer as evidenced by the existence of two very different contrasts in the MFM images recorded at room temperature. The presence of these novel skyrmionic textures as well as the understanding of their layer resolved chiral and topological properties have been investigated by micromagnetic simulations. In order to experimentally stabilize the combination of 3D skyrmion tubes and cocoons, we have elaborated metallic multilayers in which the magnetic properties, notably the anisotropy, of the magnetic films in the stacks is varied depending on their vertical position. Finally, in complement to the magnetic imaging, we also measure the magneto-resistive response of the multilayers as a function of the magnetic field, and succeed to fit its evolution using the 3D micromagnetic simulations as inputs for the magnetic configuration. The excellent agreement that is reached brings additional evidence of the presence of skyrmionic cocoons that hence can be electrically detected.
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Submitted 2 May, 2022;
originally announced May 2022.
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Spintronic THz emitters based on transition metals and semi-metals/Pt multilayers
Authors:
J. Hawecker,
E. Rongione,
A. Markou,
S. Krishnia,
F. Godel,
S. Collin,
R. Lebrun,
J. Tignon,
J. Mangeney,
T. Boulier,
J. -M. George,
C. Felser,
H. Jaffrès,
S. Dhillon
Abstract:
Spintronic terahertz (THz) emitters (STE) based on the inverse spin Hall effect in ferromagnetic/heavy metal (FM/HM) heterostructures have become important sources for THz pulse generation. The design, materials and control of these interfaces at the nanometer level has become vital to engineer their THz emission properties.In this work, we present studies of the optimization of such structures th…
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Spintronic terahertz (THz) emitters (STE) based on the inverse spin Hall effect in ferromagnetic/heavy metal (FM/HM) heterostructures have become important sources for THz pulse generation. The design, materials and control of these interfaces at the nanometer level has become vital to engineer their THz emission properties.In this work, we present studies of the optimization of such structures through a multi-pronged approach, taking advantage of material and interface engineering to enhance the THz spintronic emission. This includes: the application of multi-stacks of HM/FM junctions and their application to trilayer structures, the use of spin-sinks to simultaneously enhance the THz emitted fields and reduce the use of thick Pt layers to reduce optical absorption, and the use of semi-metals to increase the spin polarization and thus the THz emission. Through these approaches, significant enhancements of the THz field can be achieved. Importantly, taking into account the optical absorption permits to elucidate novel phenomena such as the relation between the spin diffusion length and the spin-sink using THz spectroscopy, as well as possibly distinguishing between self and interface spin-to-charge conversion in semi-metals.
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Submitted 16 March, 2022;
originally announced March 2022.
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Nonreciprocal transport in a Rashba ferromagnet, delafossite PdCoO$_2$
Authors:
Jin Hong Lee,
Takayuki Harada,
Felix Trier,
Lourdes Marcano,
Florian Godel,
Sergio Valencia,
Atsushi Tsukazaki,
Manuel Bibes
Abstract:
Rashba interfaces yield efficient spin-charge interconversion and give rise to nonreciprocal transport phenomena. Here, we report magnetotransport experiments in few-nanometer-thick films of PdCoO$_2$, a delafossite oxide known to display a large Rashba splitting and surface ferromagnetism. By analyzing the angle dependence of the first- and second-harmonic longitudinal and transverse resistivitie…
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Rashba interfaces yield efficient spin-charge interconversion and give rise to nonreciprocal transport phenomena. Here, we report magnetotransport experiments in few-nanometer-thick films of PdCoO$_2$, a delafossite oxide known to display a large Rashba splitting and surface ferromagnetism. By analyzing the angle dependence of the first- and second-harmonic longitudinal and transverse resistivities, we identify a Rashba-driven unidirectional magnetoresistance that competes with the anomalous Nernst effect below the Curie point. We estimate a Rashba coefficient of 0.75 {\pm} 0.3 eV Å and argue that our results qualify delafossites as a new family of oxides for nano-spintronics and spin-orbitronics, beyond perovskite materials.
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Submitted 29 September, 2021;
originally announced September 2021.
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Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy
Authors:
T. H. Dang,
J. Hawecker,
E. Rongione,
G. Baez Flores,
D. Q. To,
J. C. Rojas-Sanchez,
H. Nong,
J. Mangeney,
J. Tignon,
F. Godel,
S. Collin,
P. Seneor,
M. Bibes,
A. Fert,
M. Anane,
J. -M. George,
L. Vila,
M. Cosset-Cheneau,
D. Dolfi,
R. Lebrun,
P. Bortolotti,
K. Belashchenko,
S. Dhillon,
H. Jaffrès
Abstract:
Spintronic structures are extensively investigated for their spin orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to their inv…
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Spintronic structures are extensively investigated for their spin orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to their inverse spin-Hall effect properties. In particular the intrinsic inverse spin Hall effect of Pt-based systems and extrinsic inverse spin-Hall effect of Au:W and Au:Ta in NiFe/Au:(W,Ta) bilayers are investigated. The spin-charge conversion is probed by complementary techniques -- ultrafast THz time domain spectroscopy in the dynamic regime for THz pulse emission and ferromagnetic resonance spin-pumping measurements in the GHz regime in the steady state -- to determine the role played by the material properties, resistivities, spin transmission at metallic interfaces and spin-flip rates. These measurements show the correspondence between the THz time domain spectroscopy and ferromagnetic spin-pumping for the different set of samples in term of the spin mixing conductance. The latter quantity is a critical parameter, determining the strength of the THz emission from spintronic interfaces. This is further supported by ab-initio calculations, simulations and analysis of the spin-diffusion and spin relaxation of carriers within the multilayers in the time domain, permitting to determine the main trends and the role of spin transmission at interfaces. This work illustrates that time domain spectroscopy for spin-based THz emission is a powerful technique to probe spin-dynamics at active spintronic interfaces and to extract key material properties for spin-charge conversion.
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Submitted 12 December, 2020;
originally announced December 2020.
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Tailored flux pinning in superconductor/ferromagnet multilayers with engineered magnetic domain morphology from stripes to skyrmions
Authors:
X. Palermo,
N. Reyren,
S. Mesoraca,
A. V. Samokhvalov,
S. Collin,
F. Godel,
A. Sander,
K. Bouzehouane,
J. Santamaría,
V. Cros,
A. I. Buzdin,
Javier E. Villegas
Abstract:
Superconductor/Ferromagnet (S/F) hybrid systems show interesting magneto-transport behaviors that result from the transfer of properties between both constituents. For instance, magnetic memory can be transferred from the F into the S through the pinning of superconducting vortices by the ferromagnetic textures. The ability to tailor this type of induced behavior is important to broaden its range…
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Superconductor/Ferromagnet (S/F) hybrid systems show interesting magneto-transport behaviors that result from the transfer of properties between both constituents. For instance, magnetic memory can be transferred from the F into the S through the pinning of superconducting vortices by the ferromagnetic textures. The ability to tailor this type of induced behavior is important to broaden its range of applications. Here we show that engineering the F magnetization reversal allows tuning the strength of the vortex pinning (and memory) effects, as well as the field range in which they appear. This is done by using magnetic multilayers in which Co thin films are combined with different heavy metals (Ru, Ir, Pt). By choosing the materials, thicknesses, and stacking order of the layers, we can design the characteristic domain size and morphology, from out-of-plane magnetized stripe domains to much smaller magnetic skyrmions. These changes strongly affect the magneto-transport properties. The underlying mechanisms are identified by comparing the experimental results to a magnetic pinning model.
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Submitted 2 March, 2020;
originally announced March 2020.
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Long-Range Propagation and Interference of $d$-wave Superconducting Pairs in Graphene
Authors:
D. Perconte,
K. Seurre,
V. Humbert,
C. Ulysse,
A. Sander,
J. Trastoy,
V. Zatko,
F. Godel,
P. R. Kidambi,
S. Hofmann,
X. P. Zhang,
D. Bercioux,
F. S. Bergeret,
B. Dlubak,
P. Seneor,
Javier E. Villegas
Abstract:
Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here we demonstrate that those correlations propagate hundreds of nanometer, allowing for the unique observation of $d$-wave Andreev pair interferences in YBa$_2$Cu$_3$O$_7$-graphene devices that behave as a Fabry-Pérot cavity. The interferences show a…
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Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here we demonstrate that those correlations propagate hundreds of nanometer, allowing for the unique observation of $d$-wave Andreev pair interferences in YBa$_2$Cu$_3$O$_7$-graphene devices that behave as a Fabry-Pérot cavity. The interferences show as a series of pronounced conductance oscillations analogous to those originally predicted by de Gennes--Saint-James for conventional metal-superconductor junctions. The present work is pivotal to the study of exotic directional effects expected for nodal superconductivity in Dirac materials.
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Submitted 8 September, 2020; v1 submitted 24 February, 2020;
originally announced February 2020.
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Unconventional anomalous Hall effect in 3d/5d multilayers mediated by the nonlocal spin-conductivity
Authors:
T. Huong Dang,
Q. Barbedienne,
Q. D. To,
E. Rongione,
N. Reyren,
F. Godel,
S. Collin,
J. M. George,
H. Jaffrès
Abstract:
We evidenced unconventionnal Anomalous Hall Effects (AHE) in 3d/5d (Co0.2nm/Ni0.6nm)N multilayers grown on a thin Pt layer or thin Au:W alloy. The inversion observed on AHE originates from the opposite sign of the spin-orbit coupling of Pt compared to Ni. Via advanced simulations methods for the description of the spin-current profiles based on the spin-dependent Boltzmann formalism, we extracted…
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We evidenced unconventionnal Anomalous Hall Effects (AHE) in 3d/5d (Co0.2nm/Ni0.6nm)N multilayers grown on a thin Pt layer or thin Au:W alloy. The inversion observed on AHE originates from the opposite sign of the spin-orbit coupling of Pt compared to Ni. Via advanced simulations methods for the description of the spin-current profiles based on the spin-dependent Boltzmann formalism, we extracted the spin Hall angle (SHA) of Pt and (Co/Ni) as well as the relevant transport parameters. The extracted SHA for Pt, +20%, is opposite to the one of (Co/Ni), giving rise to an effective AHE inversion for thin (Co/Ni) multilayers (N < 17). The spin Hall angle in Pt is found to be larger than the one previously measured in combined spin-pumping inverse spin-Hall effect experiments in a geometry of current perpendicular to plane. Whereas magnetic proximity effects cannot explain the effect, spin-current leakage and anisotropic electron scattering at Pt/(Co,Ni) interfaces fit the experiments.
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Submitted 5 October, 2020; v1 submitted 10 February, 2019;
originally announced February 2019.
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Conductance oscillations in graphene/nanoclusters hybrid material: towards large area single electron devices
Authors:
Florian Godel,
Louis Donald Notemgnou Mouafo,
Guillaume Froehlicher,
Bernard Doudin,
Stephane Berciaud,
Yves Henry,
Jean-Francois Dayen,
David Halley
Abstract:
Large assemblies of self-organized aluminum nanoclusters embedded in an oxide layer are formed on graphene templates and used to build tunnel-junction devices. Unexpectedly, single-electron-transport behavior with well-defined Coulomb oscillations is observed for a record junction area containing millions of metal islands. Such hybrid materials offer new prospects for single-electron electronics.
Large assemblies of self-organized aluminum nanoclusters embedded in an oxide layer are formed on graphene templates and used to build tunnel-junction devices. Unexpectedly, single-electron-transport behavior with well-defined Coulomb oscillations is observed for a record junction area containing millions of metal islands. Such hybrid materials offer new prospects for single-electron electronics.
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Submitted 28 February, 2017;
originally announced March 2017.
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Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions
Authors:
F. Godel,
M. Venkata Kamalakar,
B. Doudin,
Y. Henry,
D. Halley,
J. -F. Dayen
Abstract:
We report on the fabrication and characterization of vertical spin-valve structures using a thick epitaxial MgO barrier as spacer layer and a graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show robust and scalable tunnel magnetoresistance, with several changes of sign upon varying the applied bias voltage. These findings are explained by a model of phonon-assisted trans…
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We report on the fabrication and characterization of vertical spin-valve structures using a thick epitaxial MgO barrier as spacer layer and a graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show robust and scalable tunnel magnetoresistance, with several changes of sign upon varying the applied bias voltage. These findings are explained by a model of phonon-assisted transport mechanisms that relies on the peculiarity of the band structure and spin density of states at the hybrid graphene|Ni interface.
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Submitted 7 October, 2014;
originally announced October 2014.