• F. Ajejas, Y. Sassi, W. Legrand, T. Srivastava, S. Collin, A. Vecchiola, K. Bouzehouane, N. Reyren, V. Cros, Densely packed skyrmions stabilized at zero magnetic field by indirect exchange coupling in multilayers. APL Materials. 11, 061108 (2023).
    Résumé : Room-temperature stabilization of skyrmions in magnetic multilayered systems results from a fine balance between several magnetic interactions, namely, symmetri

  • W. Amdouni, M. Fricaudet, M. Otoničar, V. Garcia, S. Fusil, J. Kreisel, H. Maghraoui-Meherzi, B. Dkhil, BiFeO3 Nanoparticles: The “Holy-Grail” of Piezo-Photocatalysts? Advanced Materials. 35, 2301841 (2023).
    Résumé : Advanced Materials, one of the world's most prestigious journals, is the home of choice for best-in-class materials science for more than 30 years.

  • J. Bréhin, Y. Chen, M. D’Antuono, S. Varotto, D. Stornaiuolo, C. Piamonteze, J. Varignon, M. Salluzzo, M. Bibes, Coexistence and coupling of ferroelectricity and magnetism in an oxide two-dimensional electron gas. Nature Physics. 19, 823 (2023).
    Résumé : Materials that simultaneously display ferroelectricity and magnetism, and are metallic, are very rare. Now, the two-dimensional electron gas in an oxide heterostructure brings all of this behaviour together.

  • E. Burgos-Parra, Y. Sassi, W. Legrand, F. Ajejas, C. Léveillé, P. Gargiani, M. Valvidares, N. Reyren, V. Cros, N. Jaouen, S. Flewett, Probing of three-dimensional spin textures in multilayers by field dependent X-ray resonant magnetic scattering. Scientific Reports. 13, 11711 (2023).
    Résumé : In multilayers of magnetic thin films with perpendicular anisotropy, domain walls can take on hybrid configurations in the vertical direction which minimize the domain wall energy, with Néel walls in the top or bottom layers and Bloch walls in some central layers. These types of textures are theoretically predicted, but their observation has remained challenging until recently, with only a few techniques capable of realizing a three dimensional characterization of their magnetization distribution. Here we perform a field dependent X-ray resonant magnetic scattering measurements on magnetic multilayers exploiting circular dichroism contrast to investigate such structures. Using a combination of micromagnetic and X-ray resonant magnetic scattering simulations along with our experimental results, we characterize the three-dimensional magnetic texture of domain walls, notably the thickness resolved characterization of the size and position of the Bloch part in hybrid walls. We also take a step in advancing the resonant scattering methodology by using measurements performed off the multilayer Bragg angle in order to calibrate the effective absorption of the X-rays, and permitting a quantitative evaluation of the out of plane (z) structure of our samples. Beyond hybrid domain walls, this approach can be used to characterize other periodic chiral structures such as skyrmions, antiskyrmions or even magnetic bobbers or hopfions, in both static and dynamic experiments.

  • A. Du, D. Zhu, K. Cao, Z. Zhang, Z. Guo, K. Shi, D. Xiong, R. Xiao, W. Cai, J. Yin, S. Lu, C. Zhang, Y. Zhang, S. Luo, A. Fert, W. Zhao, Electrical manipulation and detection of antiferromagnetism in magnetic tunnel junctions. Nature Electronics. 6, 425 (2023).
    Résumé : Antiferromagnetism of the IrMn layer in Pt/IrMn/CoFeB/MgO/CoFeB three-terminal magnetic tunnel junctions can be electrically detected using tunnelling magnetoresistance and controlled by a spin–orbit torque generated by a 0.8 ns current pulse applied across the heavy-metal platinum layer.

  • P. Dufour, T. Maroutian, M. Vallet, K. Patel, A. Chanthbouala, C. Jacquemont, L. Yedra, V. Humbert, F. Godel, B. Xu, S. Prosandeev, L. Bellaiche, M. Otoničar, S. Fusil, B. Dkhil, V. Garcia, Ferroelectric phase transitions in epitaxial antiferroelectric PbZrO3 thin films. Applied Physics Reviews. 10, 021405 (2023).
    Résumé : The archetypical antiferroelectric, PbZrO3, is currently attracting a lot of interest, but no consensus can be clearly established on the nature of its ground s

  • A. El Kanj, O. Gomonay, I. Boventer, P. Bortolotti, V. Cros, A. Anane, R. Lebrun, Antiferromagnetic magnon spintronic based on nonreciprocal and nondegenerated ultra-fast spin-waves in the canted antiferromagnet α-Fe2O3. Science Advances. 9, eadh1601 (2023).
    Résumé : Dipole-exchange antiferromagnetic spin-waves host the potential for non-reciprocal and ultra-fast magnonic devices.

  • A. Fert, M. Chshiev, A. Thiaville, H. Yang, From Early Theories of Dzyaloshinskii–Moriya Interactions in Metallic Systems to Today’s Novel Roads. Journal of the Physical Society of Japan. 92, 081001 (2023).
    Résumé : Since the early 1960’s, the discovery of Dzyaloshinskii–Moriya interaction (DMI) helped to explain the physical mechanisms behind certain magnetic phenomena, such as net moment in antiferromagnets,...

  • N. Figueiredo-Prestes, P. Tsipas, S. Krishnia, P. Pappas, J. Peiro, S. Fragkos, V. Zatko, A. Lintzeris, B. Dlubak, S. Chaitoglou, M. Heuken, N. Reyren, H. Jaffrès, P. Seneor, A. Dimoulas, J. - M. George, Large Fieldlike Spin-Orbit Torque and Magnetization Manipulation in a Fully Epitaxial van der Waals Two-Dimensional-Ferromagnet/Topological-Insulator Heterostructure Grown by Molecular-Beam Epitaxy. Physical Review Applied. 19, 014012 (2023).
    Résumé : With the development of technologies taking advantage of emerging quantum phenomena under extreme conditions of dimensionality and temperature, the search for alternative materials and heterostructure engineering has opened up on several fronts. Here, we report the magnetotransport properties of topological-insulator/two-dimensional-ferromagnet (TI/2D-FM) heterostructures composed of ${\mathrm{Cr}}_{1+\ensuremath{\delta}}{\mathrm{Te}}_{2}/{\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ stacks grown by molecular-beam epitaxy. The electrical transport measurements reveal high levels of fieldlike effective torques, up to 115 mT at a current density of ${10}^{7}\phantom{\rule{0.25em}{0ex}}\mathrm{A}/{\mathrm{cm}}^{2}$; the occurrence of interfacial magnetoresistance effects, such as the anisotropic interfacial magnetoresistance; and anomalies in the anomalous Hall effect. Furthermore, we report on complementary characterization with scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and superconducting quantum interference device measurements. Finally, magnetization reversal induced by current pulses is also reported. The reported results make the relevance of the TI/2D-FM interface evident and indicate the preservation of polarized surface states at the interface.

  • M. Grelier, F. Godel, A. Vecchiola, S. Collin, K. Bouzehouane, V. Cros, N. Reyren, R. Battistelli, H. Popescu, C. Léveillé, N. Jaouen, F. Büttner, X-ray holography of skyrmionic cocoons in aperiodic magnetic multilayers. Physical Review B. 107, L220405 (2023).
    Résumé : The development and characterization of three-dimensional topological magnetic textures has become an important topic in modern magnetism from both fundamental and technological perspectives. Here, the authors stabilize skyrmionic cocoons by engineering the properties of Pt/Co/Al based multilayers with variable Co thickness. These new textures can be observed in transmission with x-ray holography. Their coexistence with skyrmion tubes is particularly interesting as they can open new paths for three-dimensional spintronics.

  • C. Grezes, A. Kandazoglou, M. Cosset-Cheneau, L. Moreno Vicente-Arche, P. Noël, P. Sgarro, S. Auffret, K. Garello, M. Bibes, L. Vila, J. - P. Attané, Non-volatile electric control of spin-orbit torques in an oxide two-dimensional electron gas. Nature Communications. 14, 2590 (2023).
    Résumé : A central goal of spintronics is electric control of magnetism. One particularly promising method makes use of spin-orbit torques which arise due to the combination of electric current, and the intrinsic spin-orbit effect in a material. Here, Grezes et al demonstrate non-volatile electrical control of the spin-orbit torque generated at the interface between an oxide and a metal.

  • J. R. Hortensius, D. Afanasiev, L. Vistoli, M. Matthiesen, M. Bibes, A. D. Caviglia, Ultrafast activation of the double-exchange interaction in antiferromagnetic manganites. APL Materials. 11, 071107 (2023).
    Résumé : In doped manganite systems, strong electronic correlations result in rich phase diagrams where electron delocalization strongly affects the magnetic order. Here

  • S. Husain, N. Figueiredo-Prestes, O. Fayet, S. Collin, F. Godel, E. Jacquet, N. Reyren, H. Jaffrès, J. M. George, Origin of the anomalous Hall effect at the magnetic insulator/heavy metals interface. Applied Physics Letters. 122, 062403 (2023).
    Résumé : Ferrimagnetic insulators (FIMIs) are considered to be promising candidates in spin–orbit torque (SOT) devices due to their ability to propagate a spin current by magnons without Ohmic losses owing to the absence of electronic scattering. Moreover, any electrical current shunt is avoided in magnetic insulating materials. On the other hand, SOT-induced magnetization switching is generally measured through the anomalous Hall effect (AHE) in FIMI/heavy metal (HM) systems. However, the origin of AHE in FIMI/HM remains elusive since charges flow only in the HM. Here, we experimentally demonstrate that the AHE has the same origin as the spin Hall magnetoresistance (SMR). To this end, we have studied two bilayer heterostructures, Tm3Fe5O12(TmIG)/W and TmIG/Pt, where we ensure opposite spin Hall effect (SHE) signs for two heavy metals (W and Pt). The magnitudes of AHE and SMR are found to be larger for TmIG/W than TmIG/Pt. We have also evidenced the identical polarity of AHE hysteresis in both systems revealing a square dependency on the spin Hall angle whereas the current-induced magnetization switching polarity in TmIG/W is opposite to that of TmIG/Pt as expected for opposite spin Hall angle signs. Our results establish that the AHE and the spin-Hall magnetoresistance in TmIG insulating ferromagnets and heavy metal bilayers originate from the same mechanism.

  • H. Naganuma, M. Uemoto, H. Adachi, H. Shinya, I. Mochizuki, M. Kobayashi, A. Hirata, B. Dlubak, T. Ono, P. Seneor, J. Robertson, K. Amemiya, Twist pz Orbital and Spin Moment of the Wavy-Graphene/L10-FePd Moiré Interface. The Journal of Physical Chemistry C. 127, 11481 (2023).
    Résumé : A crystallographically heterogeneous moiré interface of hexagonal graphene (Gr) and a tetragonal L10-FePd alloy is bonded via van der Waals (vdW) forces. Robust interfacial perpendicular magnetic anisotropy was discovered at the L10-FePd side of the Gr/L10-FePd heterogeneous interface (H. Naganuma et al. ACS Nano, 2022, 16, 4139). This study focuses on the Gr side of the Gr/L10-FePd interface. X-ray absorption spectroscopy measurements of Gr from two different angles demonstrated that in addition to the π* orbital peak being observed at a glance incident angle (θΑ = 30°), it was also observed at a nominal incident (NI) angle (θΑ = 90°). The appearance of the π* peak at NI is attributed to the wavy Gr and strong bonding of the chemisorption-type vdW force. The densities of states of px, py, and pz from first-principles calculations indicate another reason for the π* peak at NI. The pz orbital of C twists into the x–y plane owing to its chemical bond with Fe or perturbation of the Fe ion to the C orbital. This twisted pz orbital appears near the Fermi level. Thus, the π* peak at NI can be interpreted to appear owing to three reasons: (i) the wavy Gr, (ii) the twisted pz orbital near the Fermi level, and (iii) the chemisorption-type vdW force. The X-ray magnetic circular dichroism of the C K-edge and first-principles calculations revealed that wavy Gr has a spin magnetic moment of 0.018 μB/C atoms but no orbital magnetic moment.

  • G. Orfila, D. Sanchez-Manzano, A. Arora, F. Cuellar, S. Ruiz-Gómez, S. Rodriguez-Corvillo, S. López, A. Peralta, S. J. Carreira, F. Gallego, J. Tornos, V. Rouco, J. J. Riquelme, C. Munuera, F. J. Mompean, M. Garcia-Hernandez, Z. Sefrioui, J. E. Villegas, L. Perez, A. Rivera-Calzada, C. Leon, S. Valencia, J. Santamaria, Large Magnetoresistance of Isolated Domain Walls in La2/3Sr1/3MnO3 Nanowires. Advanced Materials. 35, 2211176 (2023).
    Résumé : Advanced Materials, one of the world's most prestigious journals, is the home of choice for best-in-class materials science for more than 30 years.

  • G. A. Ramírez, W. R. Acevedo, M. Rengifo, J. M. Nuñez, M. H. Aguirre, J. Briatico, D. Rubi, Coexistence of volatile and nonvolatile memristive effects in phase-separated La0.5Ca0.5MnO3-based devices. Applied Physics Letters. 122, 063503 (2023).
    Résumé : In this work, we have investigated the coexistence of volatile and nonvolatile memristive effects in epitaxial phase-separated La0.5Ca0.5MnO3 thin films. At low temperatures (50 K), we observed volatile resistive changes arising from self-heating effects in the vicinity of a metal-to-insulator transition. At higher temperatures (140 and 200 K), we measured a combination of volatile and nonvolatile effects arising from the synergy between self-heating effects and ferromagnetic-metallic phase growth induced by an external electrical field. The results reported here add phase separated manganites to the list of materials that can electrically mimic, on the same device, the behavior of both neurons and synapses, a feature that might be useful for the development of neuromorphic computing hardware.

  • A. Román, A. Lopez Pedroso, K. Bouzehouane, J. E. Gómez, A. Butera, M. H. Aguirre, M. Medeiros Soares, C. Garcia, L. B. Steren, Magnetization reversal modes and coercive field dependence on perpendicular magnetic anisotropy in FePt thin films. Journal of Physics D: Applied Physics. 56, 395002 (2023).

  • E. Rongione, L. Baringthon, D. She, G. Patriarche, R. Lebrun, A. Lemaître, M. Morassi, N. Reyren, M. Mičica, J. Mangeney, J. Tignon, F. Bertran, S. Dhillon, P. Le Fevre, H. Jaffrès, J. - M. George, Spin-Momentum Locking and Ultrafast Spin-Charge Conversion in Ultrathin Epitaxial Bi1 − xSbx Topological Insulator. Advanced Science. 10, 2301124 (2023).
    Résumé : Spin-angle-resolved photoemission spectroscopy and THz-TDS are used to categorically demonstrate that spin-charge conversion (SCC) arises at the surface of the Bi1-xSbx topological insulator family u...

  • E. Rongione, O. Gueckstock, M. Mattern, O. Gomonay, H. Meer, C. Schmitt, R. Ramos, T. Kikkawa, M. Mičica, E. Saitoh, J. Sinova, H. Jaffrès, J. Mangeney, S. T. B. Goennenwein, S. Geprägs, T. Kampfrath, M. Kläui, M. Bargheer, T. S. Seifert, S. Dhillon, R. Lebrun, Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions. Nature Communications. 14, 1818 (2023).
    Résumé : Antiferromagnets are promising candidates to build terahertz spintronic devices. However, manipulating and detecting their terahertz spin dynamics remains key challenges. Here, Rongione et al. demonstrate both broadband and narrowband terahertz emission from an antiferromagnet/heavy metal heterostructure using spin-phonon interactions.

  • D. Sanchez-Manzano, S. Mesoraca, F. Cuellar, M. Cabero, S. Rodriguez-Corvillo, V. Rouco, F. Mompean, M. Garcia-Hernandez, J. M. Gonzalez-Calbet, C. Feuillet-Palma, N. Bergeal, J. Lesueur, C. Leon, J. - E. Villegas, J. Santamaria, Unconventional long range triplet proximity effect in planar YBa2Cu3O7/La0.7Sr0.3MnO3/YBa2Cu3O7 Josephson junctions. Superconductor Science and Technology. 36, 074002 (2023).

  • P. Sethi, D. Sanz-Hernández, F. Godel, S. Krishnia, F. Ajejas, A. Mizrahi, V. Cros, D. Marković, J. Grollier, Compensation of Anisotropy in Spin Hall Devices for Neuromorphic Applications. Physical Review Applied. 19, 064018 (2023).
    Résumé : Spintronic nano-oscillators and diodes with reduced nonlinearity benefit from low phase noise and improved device properties. Moreover, they could offer key advantages for realizing neuromorphic applications, such as spike-based neurons and frequency multiplexing in neural networks. Here, we experimentally demonstrate the reduction in nonlinearity of a spin Hall nano-oscillator (SHNO) by compensation of its effective magnetic anisotropy. The study involves optimization of $\mathrm{Co}/\mathrm{Ni}$ multilayer growth to achieve the compensation, followed by spin-diode measurements on patterned microstrips to quantify their anisotropy. The relationship between the second- $({H}_{{k}_{2}}=0.47\phantom{\rule{0.25em}{0ex}}\mathrm{mT})$ and first-order $({H}_{{k}_{1}}^{\mathrm{eff}}=\ensuremath{-}0.8\phantom{\rule{0.25em}{0ex}}\mathrm{mT})$ anisotropy fields reveals the existence of an easy cone, thereby validating the presence of compensation. Furthermore, we demonstrate a compensated spin diode that 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 nanoconstrictions of 200 and 100 nm wide. The invariance of the resonance frequency and linewidth of the compensated SHNO with applied dc current indicates the absence of nonlinearity. This independence is maintained irrespective of the applied external fields and their orientations. The compensated SHNO obtained has a linewidth of 1.1 MHz and a peak output power of up to 1 pW/MHz.

  • T. Srivastava, H. Merbouche, I. N. Krivorotov, N. Beaulieu, J. Ben Youssef, M. Muñoz, P. Che, P. Bortolotti, V. Cros, O. Klein, S. Sangiao, J. - M. De Teresa, S. O. Demokritov, V. E. Demidov, A. Anane, C. Serpico, M. d’Aquino, G. De Loubens, Identification of a Large Number of Spin-Wave Eigenmodes Excited by Parametric Pumping in Yttrium Iron Garnet Microdisks. Physical Review Applied. 19, 064078 (2023).
    Résumé : We present the parametric excitation of spin-wave modes in yttrium iron garnet (YIG) microdisks via parallel pumping. Their spectroscopy is performed using magnetic resonance force microscopy (MRFM), while their spatial profiles are determined by microfocus Brillouin light scattering (BLS). We observe that almost all the fundamental eigenmodes of an in-plane magnetized YIG microdisk, calculated using a micromagnetic eigenmode solver, can be excited using the parallel pumping scheme, as opposed to the transverse one. A comparison between the MRFM and BLS data on the one hand, and the simulations on the other hand, provides the complete spectroscopic labeling of over 40 parametrically excited modes. Our findings could be promising for spin-wave-based computation schemes, in which the amplitudes of a large number of spin-wave modes have to be controlled.

  • T. Srivastava, Y. Sassi, F. Ajejas, A. Vecchiola, I. Ngouagnia Yemeli, H. Hurdequint, K. Bouzehouane, N. Reyren, V. Cros, T. Devolder, J. - V. Kim, G. de Loubens, Resonant dynamics of three-dimensional skyrmionic textures in thin film multilayers. APL Materials. 11, 061110 (2023).
    Résumé : Skyrmions are topological magnetic solitons that exhibit a rich variety of dynamics, such as breathing and gyration, which can involve collective behavior in ar

  • Y. Sun, T. Lin, N. Lei, X. Chen, W. Kang, Z. Zhao, D. Wei, C. Chen, S. Pang, L. Hu, L. Yang, E. Dong, L. Zhao, L. Liu, Z. Yuan, A. Ullrich, C. H. Back, J. Zhang, D. Pan, J. Zhao, M. Feng, A. Fert, W. Zhao, Experimental demonstration of a skyrmion-enhanced strain-mediated physical reservoir computing system. Nature Communications. 14, 3434 (2023).
    Résumé : An energy-efficient physical reservoir is crucial for reservoir computing (RC). Here the authors demonstrate an all-electric skyrmion-enhanced strain-mediated physical RC system and achieve a benchmark chaotic time series prediction.

  • H. Wang, H. Wu, J. Zhang, Y. Liu, D. Chen, C. Pandey, J. Yin, D. Wei, N. Lei, S. Shi, H. Lu, P. Li, A. Fert, K. L. Wang, T. Nie, W. Zhao, Room temperature energy-efficient spin-orbit torque switching in two-dimensional van der Waals Fe3GeTe2 induced by topological insulators. Nature Communications. 14, 5173 (2023).
    Résumé : Magnetic random access memory (MRAM) exhibits remarkable device endurance, while also offering potential operation speed and energy efficiency improvements compared to conventional random access memory. However, challenges remain, both in terms of efficiency, and miniaturization. Here, Wang et al demonstrate a van der Waals (vdW) based spin-orbit torque switching, in a Fe3GeTe2/Bi2Te3 heterostructure, paving the way for thinner and higher efficiency spin-orbit torque based vdW MRAM.

  • V. Zatko, R. Galceran, M. Galbiati, J. Peiro, F. Godel, L. - M. Kern, D. Perconte, F. Ibrahim, A. Hallal, M. Chshiev, B. Martinez, C. Frontera, L. Balcells, P. R. Kidambi, J. Robertson, S. Hofmann, S. Collin, F. Petroff, M. - B. Martin, B. Dlubak, P. Seneor, Artificial Graphene Spin Polarized Electrode for Magnetic Tunnel Junctions. Nano Letters. 23, 34 (2023).
    Résumé : 2D materials offer the ability to expose their electronic structure to manipulations by a proximity effect. This could be harnessed to craft properties of 2D interfaces and van der Waals heterostructures in devices and quantum materials. We explore the possibility to create an artificial spin polarized electrode from graphene through proximity interaction with a ferromagnetic insulator to be used in a magnetic tunnel junction (MTJ). Ferromagnetic insulator/graphene artificial electrodes were fabricated and integrated in MTJs based on spin analyzers. Evidence of the emergence of spin polarization in proximitized graphene layers was observed through the occurrence of tunnel magnetoresistance. We deduced a spin dependent splitting of graphene’s Dirac band structure (∼15 meV) induced by the proximity effect, potentially leading to full spin polarization and opening the way to gating. The extracted spin signals illustrate the potential of 2D quantum materials based on proximity effects to craft spintronics functionalities, from vertical MTJs memory cells to logic circuits.


  • F. Ajejas, Y. Sassi, W. Legrand, S. Collin, J. P. Garcia, A. Thiaville, S. Pizzini, N. Reyren, V. Cros, A. Fert, Interfacial potential gradient modulates Dzyaloshinskii-Moriya interaction in Pt/Co/metal multilayers. Physical Review Materials. 6, L071401 (2022).
    Résumé : The actual mechanisms occurring at interfaces underlying the Dzyaloshinskii-Moriya interaction (DMI) remain a question in nanomagnetism. In this study, we investigate the origin of the interfacial DMI, aiming at estimating how independent the DMI contributions of the two interfaces of a FM layer are and what their relative weight in the effective DMI amplitude is. To this aim, we explore the correlation between the effective interfacial DMI and the metal properties, namely, atomic number, electronegativity, and the work function of the metal $M$. A clear linear relationship is found between the interfacial DMI and the work function difference at the $\mathrm{Co}/M$ interface. This result is strong evidence of the independent DMI contributions of the two interfaces for the chosen Co thickness(1 nm). It also suggests that the $\mathrm{Co}/\mathrm{Cu}$ interface bears no interfacial DMI. These findings can guide the optimization of the magnetic properties of future devices.

  • L. Baringthon, T. H. Dang, H. Jaffrès, N. Reyren, J. - M. George, M. Morassi, G. Patriarche, A. Lemaitre, F. Bertran, P. le Fèvre, Topological surface states in ultrathin Bi1–xSbx layers. Physical Review Materials. 6, 074204 (2022).
    Résumé : Topological insulator spin-polarized surface states are attractive for spintronic applications, in particular for spin-charge current interconversion, where extremely high conversion efficiencies are predicted. However, the contribution of topologically trivial bulk states is often disregarded although it may play a crucial role in the experimental results and extracted conversion efficiencies. The presence of bulk states at the Fermi level can be avoided by increasing the gap using the confinement effect appearing as the film thickness is reduced. We address this topic by growing ${\mathrm{Bi}}_{1\ensuremath{-}\mathrm{x}}{\mathrm{Sb}}_{x}$ thin films (2.5--15 nm) by molecular beam epitaxy on InSb, ${\mathrm{BaF}}_{2}$, and Si substrates. The surface electronic band structure is studied by angle-resolved photoemission spectroscopy. Two ${\mathrm{Bi}}_{1\ensuremath{-}\mathrm{x}}{\mathrm{Sb}}_{x}$ surface states are observed in the gap for several Sb concentrations and thicknesses, across the topological insulator phase, scanning $x$ between 7% and 30%. Tight-binding calculations of the surface states are in good agreement with the experiments, revealing their polarized nature. Surface states are still present at the \ensuremath{\Gamma} point for the thinnest films (2.5 nm), suggesting highly confined polarized states at the surface.

  • A. - C. Basaran, C. Monton, J. Trastoy, R. Bernard, K. Bouzehouane, J. E. Villegas, I. - K. Schuller, Emergence of exchange bias and giant coercive field enhancement by internal magnetic frustration in La0.67Sr0.33MnO3 thin films. Journal of Magnetism and Magnetic Materials. 550, 169077 (2022).
    Résumé : We have studied the influence of controlled defects on the magnetic properties of La0.67Sr0.33MnO3 (LSMO) thin films. We used 100 nm thick epitaxial L…

  • F. Bernardini, L. Iglesias, M. Bibes, A. Cano, Thin-Film Aspects of Superconducting Nickelates. Frontiers in Physics. 10, 828007 (2022).
    Résumé : The discovery of superconductivity in infinite-layer nickelates has attracted much attention due to their association to the high-$T_c$ cuprates. Cuprate superconductivity was first demonstrated in bulk samples and subsequently in thin films. In the nickelates, however, the situation has been reversed: although surging as a bulk phenomenon, nickelate superconductivity has only been reported in thin films so far. At the same time, the specifics of infinite-layer nickelates yield distinct interface and surface effects that determine their bulk vs thin-film behavior. In this paper, we provide an overview on these important aspects.

  • X. Chen, F. Abreu Araujo, M. Riou, J. Torrejon, D. Ravelosona, W. Kang, W. Zhao, J. Grollier, D. Querlioz, Forecasting the outcome of spintronic experiments with Neural Ordinary Differential Equations. Nature Communications. 13, 1016 (2022).
    Résumé : Deep learning has an increasing impact to assist research. Here, authors show that a dynamical neural network, trained on a minimal amount of data, can predict the behaviour of spintronic devices with high accuracy and an extremely efficient simulation time.

  • D. V. Christensen, R. Dittmann, B. Linares-Barranco, A. Sebastian, M. Le Gallo, A. Redaelli, S. Slesazeck, T. Mikolajick, S. Spiga, S. Menzel, I. Valov, G. Milano, C. Ricciardi, S. - J. Liang, F. Miao, M. Lanza, T. J. Quill, S. T. Keene, A. Salleo, J. Grollier, D. Marković, A. Mizrahi, P. Yao, J. J. Yang, G. Indiveri, J. P. Strachan, S. Datta, E. Vianello, A. Valentian, J. Feldmann, X. Li, W. H. P. Pernice, H. Bhaskaran, S. Furber, E. Neftci, F. Scherr, W. Maass, S. Ramaswamy, J. Tapson, P. Panda, Y. Kim, G. Tanaka, S. Thorpe, C. Bartolozzi, T. A. Cleland, C. Posch, S. Liu, G. Panuccio, M. Mahmud, A. N. Mazumder, M. Hosseini, T. Mohsenin, E. Donati, S. Tolu, R. Galeazzi, M. - E. Christensen, S. Holm, D. Ielmini, N. Pryds, 2022 roadmap on neuromorphic computing and engineering. Neuromorphic Computing and Engineering. 2, 022501 (2022).

  • A. V. Chumak, P. Kabos, M. Wu, C. Abert, C. Adelmann, A. O. Adeyeye, J. Åkerman, F. G. Aliev, A. Anane, A. Awad, C. H. Back, A. Barman, G. E. W. Bauer, M. Becherer, E. N. Beginin, V. A. S. V. Bittencourt, Y. M. Blanter, P. Bortolotti, I. Boventer, D. A. Bozhko, S. A. Bunyaev, J. J. Carmiggelt, R. R. Cheenikundil, F. Ciubotaru, S. Cotofana, G. Csaba, O. V. Dobrovolskiy, C. Dubs, M. Elyasi, K. G. Fripp, H. Fulara, I. A. Golovchanskiy, C. Gonzalez-Ballestero, P. Graczyk, D. Grundler, P. Gruszecki, G. Gubbiotti, K. Guslienko, A. Haldar, S. Hamdioui, R. Hertel, B. Hillebrands, T. Hioki, A. Houshang, C. - M. Hu, H. Huebl, M. Huth, E. Iacocca, M. B. Jungfleisch, G. N. Kakazei, A. Khitun, R. Khymyn, T. Kikkawa, M. Kläui, O. Klein, J. W. Kłos, S. Knauer, S. Koraltan, M. Kostylev, M. Krawczyk, I. N. Krivorotov, V. V. Kruglyak, D. Lachance-Quirion, S. Ladak, R. Lebrun, Y. Li, M. Lindner, R. Macêdo, S. Mayr, G. A. Melkov, S. Mieszczak, Y. Nakamura, H. T. Nembach, A. A. Nikitin, S. A. Nikitov, V. Novosad, J. A. Otálora, Y. Otani, A. Papp, B. Pigeau, P. Pirro, W. Porod, F. Porrati, H. Qin, B. Rana, T. Reimann, F. Riente, O. Romero-Isart, A. Ross, A. V. Sadovnikov, A. R. Safin, E. Saitoh, G. Schmidt, H. Schultheiss, K. Schultheiss, A. A. Serga, S. Sharma, J. M. Shaw, D. Suess, O. Surzhenko, K. Szulc, T. Taniguchi, M. Urbánek, K. Usami, A. B. Ustinov, T. van der Sar, S. van Dijken, V. I. Vasyuchka, R. Verba, S. V. Kusminskiy, Q. Wang, M. Weides, M. Weiler, S. Wintz, S. P. Wolski, X. Zhang, Advances in Magnetics Roadmap on Spin-Wave Computing. IEEE Transactions on Magnetics. 58, 1-72 (2022).
    Résumé : Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors, which covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with the Boolean digital data, unconventional approaches, such as neuromorphic computing, and the progress toward magnon-based quantum computing. This article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.
    Mots-clés : Computing, data processing, Logic gates, Magnetic domains, magnon, Magnonics, Nanoscale devices, Physics, Quantum computing, spin wave, Three-dimensional displays.

  • S. Das, A. Ross, X. X. Ma, S. Becker, C. Schmitt, F. van Duijn, E. F. Galindez-Ruales, F. Fuhrmann, M. - A. Syskaki, U. Ebels, V. Baltz, A. - L. Barra, H. Y. Chen, G. Jakob, S. X. Cao, J. Sinova, O. Gomonay, R. Lebrun, M. Kläui, Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3. Nature Communications. 13, 6140 (2022).
    Résumé : Antiferromagnets have attracted interest for spin-based information processing due to their resilience to stray magnetic fields and extremely rapid spin dynamics, however, long range spin wave transport has only been shown in one type of antiferromagnet thus far. Here, Das et al demonstrate long range spin wave transport in antiferromagnetic YFeO3.

  • M. Deb, E. Popova, H. Jaffrès, N. Keller, M. Bargheer, Polarization-dependent subpicosecond demagnetization in iron garnets. Physical Review B. 106, 184416 (2022).
    Résumé : Controlling the magnetization dynamics at the fastest speed is a major issue of fundamental condensed matter physics and its applications for data storage and processing technologies. It requires a deep understanding of the interactions between the degrees of freedom in solids, such as spin, electron, and lattice as well as their responses to external stimuli. In this paper, we systematically investigate the fluence dependence of ultrafast magnetization dynamics induced by below-bandgap ultrashort laser pulses in the ferrimagnetic insulators ${\mathrm{Bi}}_{x}{\mathrm{Y}}_{3\ensuremath{-}x}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ with $1\ensuremath{\le}{x}_{\mathrm{Bi}}\ensuremath{\le}3$. We demonstrate subpicosecond demagnetization dynamics in this material followed by a very slow remagnetization process. We prove that this demagnetization results from an ultrafast heating of iron garnets by two-photon absorption (TPA), suggesting a phonon-magnon thermalization time of $\ensuremath{\le}0.6$ ps. We explain the slow remagnetization timescale by the low phonon heat conductivity in garnets. Additionally, we show that the amplitudes of the demagnetization, optical change, and lattice strain can be manipulated by changing the ellipticity of the pump pulses. We explain this phenomenon considering the TPA circular dichroism. These findings open exciting prospects for ultrafast manipulation of spin, charge, and lattice dynamics in magnetic insulators by ultrafast nonlinear optics.

  • M. Deb, E. Popova, H. Jaffrès, N. Keller, M. Bargheer, Controlling High-Frequency Spin-Wave Dynamics Using Double-Pulse Laser Excitation. Physical Review Applied. 18, 044001 (2022).
    Résumé : Manipulating spin waves is highly required for the development of innovative data transport and processing technologies. Recently, the possibility of triggering high-frequency standing spin waves in magnetic insulators using femtosecond laser pulses was discovered, raising the question about how one can manipulate their dynamics. Here we explore this question by investigating the ultrafast magnetization and spin-wave dynamics induced by double-pulse laser excitation. We demonstrate a suppression or enhancement of the amplitudes of the standing spin waves by precisely tuning the time delay between the two pulses. The results can be understood as the constructive or destructive interference of the spin waves induced by the first and second laser pulses. Our findings open exciting perspectives towards generating single-mode standing spin waves that combine high frequency with large amplitude and low magnetic damping.

  • A. Finco, A. Haykal, S. Fusil, P. Kumar, P. Dufour, A. Forget, D. Colson, J. - Y. Chauleau, M. Viret, N. Jaouen, V. Garcia, V. Jacques, Imaging Topological Defects in a Noncollinear Antiferromagnet. Physical Review Letters. 128, 187201 (2022).
    Résumé : Using a scanning quantum magnetometer based on a single nitrogen vacancy center in diamond, the formation of topological defects emerging from the cycloidal antiferromagnetic order at the surface of bulk BiFeO${}_{3}$ crystals has been imaged.

  • Y. Fu, J. Li, J. Papin, P. Noël, S. Teresi, M. Cosset-Chéneau, C. Grezes, T. Guillet, C. Thomas, Y. - M. Niquet, P. Ballet, T. Meunier, J. - P. Attané, A. Fert, L. Vila, Bilinear Magnetoresistance in HgTe Topological Insulator: Opposite Signs at Opposite Surfaces Demonstrated by Gate Control. Nano Letters. 22, 7867 (2022).
    Résumé : Spin–orbit effects appearing in topological insulators (TI) and at Rashba interfaces are currently revolutionizing how we can manipulate spins and have led to several newly discovered effects, from spin-charge interconversion and spin–orbit torques to novel magnetoresistance phenomena. In particular, a puzzling magnetoresistance has been evidenced as bilinear in electric and magnetic fields. Here, we report the observation of bilinear magnetoresistance (BMR) in strained HgTe, a prototypical TI. We show that both the amplitude and sign of this BMR can be tuned by controlling with an electric gate the relative proportions of the opposite contributions of opposite surfaces. At magnetic fields of 1 T, the magnetoresistance is of the order of 1% and has a larger figure of merit than previously measured TIs. We propose a theoretical model giving a quantitative account of our experimental data. This phenomenon, unique to TI, offers novel opportunities to tune their electrical response for spintronics.

  • S. Fusil, J. - Y. Chauleau, X. Li, J. Fischer, P. Dufour, C. Léveillé, C. Carrétéro, N. Jaouen, M. Viret, A. Gloter, V. Garcia, Polar Chirality in BiFeO3 Emerging from A Peculiar Domain Wall Sequence. Advanced Electronic Materials. 8, 2101155 (2022).
    Résumé : The polar chirality of striped-domain multiferroic thin films of BiFeO3 is associated with a complex set of ferroelectric domain walls. Interestingly, the complete polar winding proceeds as an altern...

  • M. Grelier, F. Godel, A. Vecchiola, S. Collin, K. Bouzehouane, A. Fert, V. Cros, N. Reyren, Three-dimensional skyrmionic cocoons in magnetic multilayers. Nature Communications. 13, 6843 (2022).
    Résumé : Three dimensional topological spin textures, such as hopfions and skyrmion tubes, have seen a surge of interest for their potential technological applications. They offer greater flexibility than their two dimensional counterparts, but have been hampered by the limited material platforms. Here, Grelier et al. look at aperiodic multilayers, and observe a three dimensional skyrmionic cocoon.

  • V. Haspot, P. Noël, J. - P. Attané, L. Vila, M. Bibes, A. Anane, A. Barthélémy, Temperature dependence of the Gilbert damping of La0.7Sr0.3MnO3 thin films. Physical Review Materials. 6, 024406 (2022).
    Résumé : Due to its half metallic nature, ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ is an attractive highly correlated electronic system to obtain ultralow magnetic damping. In this paper we analyze the temperature and thickness dependence of the damping of the magnetization dynamic of epitaxial thin ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ films. Our analysis reveals that the damping encompasses resistivelike and conductivelike contributions, as in transition metal ferromagnets. The data also show a large increase of the ferromagnetic resonance linewidth at low temperature, a feature that we ascribe to the presence of a dead layer, insulating and magnetically active, that behaves like a spin sink. The associated spin-pumping term shows a strong temperature dependence, linked to that of the spin mixing conductance. By clarifying some unexplored aspects of spin dynamics in half-metallic manganites, our results contribute to the progress in the burgeoning field of oxide spin orbitronics.

  • 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, Spintronic THz emitters based on transition metals and semi-metals/Pt multilayers. Applied Physics Letters. 120, 122406 (2022).
    Résumé : Spintronic terahertz (THz) emitters 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 have 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 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, 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.

  • H. Humbert, R. El Hage, G. Krieger, G. Sanchez-Santolino, A. Sander, S. Collin, J. Trastoy, J. Briatico, J. Santamaria, D. Preziosi, J. E. Villegas, An Oxygen Vacancy Memristor Ruled by Electron Correlations. Advanced Science. 9, 2201753 (2022).
    Résumé : A reversible oxygen exchange at the interface between an amorphous metal (Mo80Si20) and a strongly correlated oxide (NdNiO3, NNO) yields strong resistive switching effects. Interestingly the metal-to...

  • L. Joly, F. Scheurer, P. Ohresser, B. Kengni-Zanguim, J. - F. Dayen, P. Seneor, B. Dlubak, F. Godel, D. Halley, X-ray magnetic dichroism and tunnel magneto-resistance study of the magnetic phase in epitaxial CrVO x nanoclusters. Journal of Physics: Condensed Matter. 34, 175801 (2022).

  • J. H. Lee, L. Marcano, R. Aeschlimann, M. - A. Mawass, C. Luo, A. Gloter, J. Varignon, F. Radu, S. Valencia, M. Bibes, Strain tuning of Néel temperature in YCrO3 epitaxial thin films. APL Materials. 10, 081101 (2022).
    Résumé : Epitaxial strain is a useful handle to engineer the physical properties of perovskite oxide materials. Here, we apply it to orthorhombic chromites that are a family of antiferromagnets showing fruitful functionalities as well as strong spin–lattice coupling via antisymmetric exchange interaction along Cr–O–Cr bonds. Using pulsed laser deposition, we grow YCrO3 thin films on various substrates imposing strain levels in the range from −1.8% to +0.3%. The films are stoichiometric with a 3+ valence for Cr both within the films and at their surface. They display an antiferromagnetic spin order below their Néel temperature, which we show can be strongly tuned by epitaxial strain with a slope of −8.54 K/%. A dimensionless figure of merit (defined as the slope normalized by the Néel temperature of bulk) is determined to be 6.1, which is larger than that of other perovskites, such as manganites (5.5), ferrites (2.3), or nickelates (4.6). Density functional theory simulations bring insight into the role of Cr–O bond lengths and oxygen octahedral rotations on the observed behavior. Our results shed light on orthorhombic chromites that may offer an energy-efficient piezo-spintronic operation.

  • W. Legrand, Y. Sassi, F. Ajejas, S. Collin, L. Bocher, H. Jia, M. Hoffmann, B. Zimmermann, S. Blügel, N. Reyren, V. Cros, A. Thiaville, Spatial extent of the Dzyaloshinskii-Moriya interaction at metallic interfaces. Physical Review Materials. 6, 024408 (2022).
    Résumé : Inversion-asymmetric stacks of metallic magnetic layers have often been exploited to control the chiral noncollinear ordering of their magnetic moments. Here, the authors investigate the interfacial aspects of the Dzyaloshinskii-Moriya interaction, giving rise to this chiral magnetic ordering, and quantify its contributions to within a couple atomic layers. This observation is further supported by first-principles calculations. The confirmation of the short spatial extent of the interfacial DMI is expected to enable the synthesis of dense magnetic multilayers and to offer further possibilities for engineering their spintronic properties.

  • N. Leroux, A. De Riz, D. Sanz-Hernández, D. Marković, A. Mizrahi, J. Grollier, Convolutional neural networks with radio-frequency spintronic nano-devices. Neuromorphic Computing and Engineering. 2, 034002 (2022).

  • J. Liang, M. Chshiev, A. Fert, H. Yang, Gradient-Induced Dzyaloshinskii–Moriya Interaction. Nano Letters. 22, 10128 (2022).
    Résumé : The Dzyaloshinskii–Moriya interaction (DMI) that arises in the magnetic systems with broken inversion symmetry plays an essential role in topological spintronics. Here, by means of atomistic spin calculations, we study an intriguing type of DMI (g-DMI) that emerges in the films with composition gradient. We show that both the strength and chirality of g-DMI can be controlled by the composition gradient even in the disordered system. The layer-resolved analysis of g-DMI unveils its additive nature inside the bulk layers and clarifies the linear thickness dependence of g-DMI observed in experiments. Furthermore, we demonstrate the g-DMI-induced chiral magnetic structures, such as spin spirals and skyrmions, and the g-DMI driven field-free spin–orbit torque (SOT) switching, both of which are crucial toward practical device application. These results elucidate the underlying mechanisms of g-DMI and open up a new way to engineer the topological magnetic textures.

  • C. Léveillé, E. Burgos-Parra, Y. Sassi, F. Ajejas, V. Chardonnet, E. Pedersoli, F. Capotondi, G. De Ninno, F. Maccherozzi, S. Dhesi, D. M. Burn, G. van der Laan, O. S. Latcham, A. V. Shytov, V. V. Kruglyak, E. Jal, V. Cros, J. - Y. Chauleau, N. Reyren, M. Viret, N. Jaouen, Ultrafast time-evolution of chiral Néel magnetic domain walls probed by circular dichroism in x-ray resonant magnetic scattering. Nature Communications. 13, 1412 (2022).
    Résumé : There is interest in encoding of information in complex spin structures present in magnetic systems, such as domain walls. Here, Léveillé et al study the ultrafast dynamics of chiral domain walls, and show the emergence of a transient spin chiral texture at the domain wall.

  • S. Mallik, G. C. Ménard, G. Saïz, I. Gilmutdinov, D. Vignolles, C. Proust, A. Gloter, N. Bergeal, M. Gabay, M. Bibes, From Low-Field Sondheimer Oscillations to High-Field Very Large and Linear Magnetoresistance in a SrTiO3-Based Two-Dimensional Electron Gas. Nano Letters. 22, 65 (2022).
    Résumé : Quantum materials harbor a cornucopia of exotic transport phenomena challenging our understanding of condensed matter. Among these, a giant, nonsaturating linear magnetoresistance (MR) has been reported in various systems, from Weyl semimetals to topological insulators. Its origin is often ascribed to unusual band structure effects, but it may also be caused by extrinsic sample disorder. Here, we report a very large linear MR in a SrTiO3 two-dimensional electron gas and, by combining transport measurements with electron spectromicroscopy, show that it is caused by nanoscale inhomogeneities that are self-organized during sample growth. Our data also reveal semiclassical Sondheimer oscillations arising from interferences between helicoidal electron trajectories, from which we determine the 2DEG thickness. Our results bring insight into the origin of linear MR in quantum materials, expand the range of functionalities of oxide 2DEGs, and suggest exciting routes to explore the interaction of linear MR with features like Rashba spin–orbit coupling.

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