• 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

  • 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. 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • S. Mallik, G. C. Ménard, G. Saïz, H. Witt, J. Lesueur, A. Gloter, L. Benfatto, M. Bibes, N. Bergeal, Superfluid stiffness of a KTaO3-based two-dimensional electron gas. Nature Communications. 13, 4625 (2022).
    Résumé : Heterostructures based on (111)-oriented KTaO3crystals are a new platform for studying oxide interfaces. Gate-tunable superconductivity in 2D electron gases at the surface of (111)-oriented KTaO3is now reported, with the superconducting transition being of the Berezinskii-Kosterlitz-Thouless type.

  • D. Marković, Synchronization by memristors. Nature Materials. 21, 4-5 (2022).
    Résumé : Integration of memristors in a chain of nano-constriction spintronic oscillators allows for individual control of oscillation frequencies and emerging synchronization patterns. The control of such synchronization could enable learning through association like neurons in the brain.

  • D. Marković, M. W. Daniels, P. Sethi, A. D. Kent, M. D. Stiles, J. Grollier, Easy-plane spin Hall nano-oscillators as spiking neurons for neuromorphic computing. Physical Review B. 105, 014411 (2022).
    Résumé : Ferromagnetic nanoconstrictions can serve as integrate-and-fire neurons, communicating via spin-wave pulses analogous to neural spikes. The nanoconstriction geometry leads to easy-plane oscillators which manifest phase dynamics analogous to damped driven oscillators. The authors propose a sample geometry where nanoconstrictions undergo phase slips and produce pulses of spin-wave signals when triggered by a small spin torque. They show with the help of macrospin modeling and micromagnetic simulations that these spin-wave pulses can excite other nanoconstriction neurons and that they possess the basic fan-in and fan-out capability required for neuromorphic systems.

  • P. Martin, B. Dlubak, R. Mattana, P. Seneor, M. - B. Martin, T. Henner, F. Godel, A. Sander, S. Collin, L. Chen, S. Suffit, F. Mallet, P. Lafarge, M. L. Della Rocca, A. Droghetti, C. Barraud, Combined spin filtering actions in hybrid magnetic junctions based on organic chains covalently attached to graphene. Nanoscale. 14, 12692 (2022).

  • P. Martin, B. Dlubak, P. Seneor, R. Mattana, M. - B. Martin, P. Lafarge, F. Mallet, M. L. Della Rocca, S. M. - M. Dubois, J. - C. Charlier, C. Barraud, Organic–Inorganic Hybrid Interfaces for Spin Injection into Carbon Nanotubes and Graphene. Advanced Quantum Technologies. 5, 2100166 (2022).
    Résumé : In this review, the recent progresses, understandings, and results obtained with the implementation of hybrid organic molecules/ferromagnetic metal interfaces in spintronics devices based on graphene...

  • H. Merbouche, B. Divinskiy, K. O. Nikolaev, C. Kaspar, W. H. P. Pernice, D. Gouéré, R. Lebrun, V. Cros, J. Ben Youssef, P. Bortolotti, A. Anane, S. O. Demokritov, V. E. Demidov, Giant nonlinear self-phase modulation of large-amplitude spin waves in microscopic YIG waveguides. Scientific Reports. 12, 7246 (2022).
    Résumé : Nonlinear self-phase modulation is a universal phenomenon responsible, for example, for the formation of propagating dynamic solitons. It has been reported for waves of different physical nature. However its direct experimental observation for spin waves has been challenging. Here we show that exceptionally strong phase modulation can be achieved for spin waves in microscopic waveguides fabricated from nanometer-thick films of magnetic insulator, which support propagation of spin waves with large amplitudes corresponding to angles of magnetization precession exceeding 10°. At these amplitudes, the nonstationary nonlinear dynamic response of the spin system causes an extreme broadening of the spectrum of spin-wave pulses resulting in a strong spatial variation of the spin-wave wavelength and a temporal variation of the spin-wave phase across the pulse. Our findings demonstrate great complexity of nonlinear wave processes in microscopic magnetic structures and importance of their understanding for technical applications of spin waves in integrated devices.

  • H. Naganuma, M. Nishijima, H. Adachi, M. Uemoto, H. Shinya, S. Yasui, H. Morioka, A. Hirata, F. Godel, M. - B. Martin, B. Dlubak, P. Seneor, K. Amemiya, Unveiling a Chemisorbed Crystallographically Heterogeneous Graphene/L10-FePd Interface with a Robust and Perpendicular Orbital Moment. ACS Nano. 16, 4139 (2022).
    Résumé : A crystallographically heterogeneous interface was fabricated by growing hexagonal graphene (Gr) using chemical vapor deposition (CVD) on a tetragonal FePd epitaxial film grown by magnetron sputtering. FePd was alternately arranged with Fe and Pd in the vertical direction, and the outermost surface atom was identified primarily as Fe rather than Pd. This means that FePd has a high degree of L10-ordering, and the outermost Fe bonds to the carbon of Gr at the interface. When Gr is grown by CVD, the crystal orientation of hexagonal Gr toward tetragonal L10-FePd selects an energetically stable structure based on the van der Waals (vdW) force. The atomic relationship of Gr/L10-FePd, which is an energetically stable interface, was unveiled theoretically and experimentally. The Gr armchair axis was parallel to FePd [100]L10, where Gr was under a small strain by chemical bonding. Focusing on the interatomic distance between the Gr and FePd layers, the distance was theoretically and experimentally determined to be approximately 0.2 nm. This shorter distance (≈0.2 nm) can be explained by the chemisorption-type vdW force of strong orbital hybridization, rather than the longer distance (≈0.38 nm) of the physisorption-type vdW force. Notably, depth-resolved X-ray magnetic circular dichroism analyses revealed that the orbital magnetic moment (Ml) of Fe in FePd emerged at the Gr/FePd interface (@inner FePd: Ml = 0.16 μB → @Gr/FePd interface: Ml = 0.32 μB). This interfacially enhanced Ml showed obvious anisotropy in the perpendicular direction, which contributed to interfacial perpendicular magnetic anisotropy (IPMA). Moreover, the interfacially enhanced Ml and interfacially enhanced electron density exhibited robustness. It is considered that the shortening of the interatomic distance produces a robust high electron density at the interface, resulting in a chemisorption-type vdW force and orbital hybridization. Eventually, the robust interfacial anisotropic Ml emerged at the crystallographically heterogeneous Gr/L10-FePd interface. From a practical viewpoint, IPMA is useful because it can be incorporated into the large bulk perpendicular magnetic anisotropy (PMA) of L10-FePd. A micromagnetic simulation assuming both PMA and IPMA predicted that perpendicularly magnetized magnetic tunnel junctions (p-MTJs) using Gr/L10-FePd could realize 10-year data retention in a small recording layer with a circular diameter and thickness of 10 and 2 nm, respectively. We unveiled the energetically stable atomic structure in the crystallographically heterogeneous interface, discovered the emergence of the robust IPMA, and predicted that the Gr/L10-FePd p-MTJ is significant for high-density X nm generation magnetic random-access memory (MRAM) applications.

  • B. Quinard, F. Godel, M. Galbiati, V. Zatko, A. Sander, A. Vecchiola, S. Collin, K. Bouzehouane, F. Petroff, R. Mattana, M. - B. Martin, B. Dlubak, P. Seneor, A ferromagnetic spin source grown by atomic layer deposition. Applied Physics Letters. 120, 213503 (2022).
    Résumé : We report on the growth of a ferromagnetic cobalt electrode by atomic layer deposition (ALD) and demonstrate it as a functional spin source in complete magnetic tunnel junctions (MTJs). Using an in situ protocol, we integrate a reference tunnel barrier on top of the ALD cobalt spin source stabilizing its metallic nature and allowing further characterization. The cobalt layer, grown in mbar conditions with chemical precursors, is assessed to be metallic and ferromagnetic using both x-ray photoelectron spectroscopy and superconducting quantum interference device magnetometry measurements. Atomic force microscopy tapping and conductive tip mode analyses reveal a very flat film with low roughness (0.2 nm RMS) with a high homogeneity of surface conductivity matching the best reference samples grown by sputtering. We finally evaluate its behavior in full MTJ spin valves, using a reference spin analyzer to highlight that the ALD grown layer is, indeed, spin polarized and can act as a functional spintronics electrode. This result opens the perspective of exploiting the benefits of ALD (such as the wide area low-cost process, extreme conformality, layer by layer growth of heterostructures, area selectivity, etc.) for spintronics applications.

  • M. Romera, P. Talatchian, S. Tsunegi, K. Yakushiji, A. Fukushima, H. Kubota, S. Yuasa, V. Cros, P. Bortolotti, M. Ernoult, D. Querlioz, J. Grollier, Binding events through the mutual synchronization of spintronic nano-neurons. Nature Communications. 13, 883 (2022).
    Résumé : Spin-torque nano-oscillators have sparked interest for their potential in neuromorphic computing, however concrete demonstration are limited. Here, Romera et al show how spin-torque nano-oscillators can mutually synchronise and recognize temporal patterns, much like neurons, illustrating their potential for neuromorphic computing.

  • E. Rongione, S. Fragkos, L. Baringthon, J. Hawecker, E. Xenogiannopoulou, P. Tsipas, C. Song, M. Mičica, J. Mangeney, J. Tignon, T. Boulier, N. Reyren, R. Lebrun, J. - M. George, P. L. Fèvre, S. Dhillon, A. Dimoulas, H. Jaffrès, Ultrafast Spin-Charge Conversion at SnBi2Te4/Co Topological Insulator Interfaces Probed by Terahertz Emission Spectroscopy. Advanced Optical Materials. 10, 2102061 (2022).
    Résumé : THz emission spectroscopy has an increasingly major role to play in the investigation of the spin-to-charge conversion phenomena in the time domain in SnBi2Te4 topological insulator/Co interfaces. Th...

  • A. Ross, R. Lebrun, O. Gomonay, J. Sinova, D. A. Kay, D. A. Grave, A. Rothschild, M. Kläui, Magnon transport in the presence of antisymmetric exchange in a weak antiferromagnet. Journal of Magnetism and Magnetic Materials. 543, 168631 (2022).
    Résumé : The Dzyaloshinskii-Moriya interaction (DMI) is at the heart of many modern developments in the research field of spintronics. DMI is known to generate…

  • V. I. Safarov, I. V. Rozhansky, Z. Zhou, B. Xu, Z. Wei, Z. - G. Wang, Y. Lu, H. Jaffrès, H. - J. Drouhin, Recombination Time Mismatch and Spin Dependent Photocurrent at a Ferromagnetic-Metal–Semiconductor Tunnel Junction. Physical Review Letters. 128, 057701 (2022).
    Résumé : We report on carrier dynamics in a spin photodiode based on a ferromagnetic-metal--GaAs tunnel junction. We show that the helicity-dependent current is determined not only by the electron spin polarization and spin asymmetry of the tunneling but in great part by a dynamical factor resulting from the competition between tunneling and recombination in the semiconductor, as well as by a specific quantity: the charge polarization of the photocurrent. The two latter factors can be efficiently controlled through an electrical bias. Under longitudinal magnetic field, we observe a strong increase of the signal arising from inverted Hanle effect, which is a fingerprint of its spin origin. Our approach represents a radical shift in the physical description of this family of emerging spin devices.

  • D. Sanchez-Manzano, S. Mesoraca, F. A. Cuellar, M. Cabero, V. Rouco, G. Orfila, X. Palermo, A. Balan, L. Marcano, A. Sander, M. Rocci, J. Garcia-Barriocanal, F. Gallego, J. Tornos, A. Rivera, F. Mompean, M. Garcia-Hernandez, J. M. Gonzalez-Calbet, C. Leon, S. Valencia, C. Feuillet-Palma, N. Bergeal, A. I. Buzdin, J. Lesueur, J. E. Villegas, J. Santamaria, Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet. Nature Materials. 21, 188 (2022).
    Résumé : Josephson coupling over micrometres and at tens of kelvins is demonstrated across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7.

  • Z. Shao, J. Liang, Q. Cui, M. Chshiev, A. Fert, T. Zhou, H. Yang, Multiferroic materials based on transition-metal dichalcogenides: Potential platform for reversible control of Dzyaloshinskii-Moriya interaction and skyrmion via electric field. Physical Review B. 105, 174404 (2022).
    Résumé : Exploring novel two-dimensional multiferroic materials that can realize electric-field control of two-dimensional magnetism has become an emerging topic in spintronics. Using first-principles calculations, we demonstrate that nonmetallic bilayer transition-metal dichalcogenides can be an ideal platform for building multiferroics by intercalated magnetic atoms. Moreover, we unveil that with Co intercalated bilayer ${\mathrm{MoS}}_{2}, \mathrm{Co}{(\mathrm{Mo}{\mathrm{S}}_{2})}_{2}$, two energetically degenerate states with opposite chirality of Dzyaloshinskii-Moriya interaction are the ground states, indicating electric-field control of the chirality of topological magnetic objects such as skyrmions can be realized in this type of materials by reversing the electric polarization. These findings pave the way for electric-field control of topological magnetism in two-dimensional multiferroics with intrinsic magnetoelectric coupling.

  • A. Sidi El Valli, V. Iurchuk, G. Lezier, I. Bendjeddou, R. Lebrun, N. Lamard, A. Litvinenko, J. Langer, J. Wrona, L. Vila, R. Sousa, I. L. Prejbeanu, B. Dieny, U. Ebels, Size-dependent enhancement of passive microwave rectification in magnetic tunnel junctions with perpendicular magnetic anisotropy. Applied Physics Letters. 120, 012406 (2022).
    Résumé : Spintronic rf detectors are efficient nanoscale counterparts to conventional semiconductor-based components for energy harvesting and wireless communication at low input power. Here, we report on the optimization of the rectified output dc voltage using magnetic tunnel junctions (MTJs) with strong perpendicular anisotropy of both the polarizing and free layers. The magnetization of the polarizing layer is fixed out-of-plane, while the free layer thickness is adjusted so that its magnetization orientation changes from in-plane to out-of-plane. Rectification dc output voltages in the mV range are obtained for moderate rf source powers with a signal-to-noise ratio of 26–39 dB for Prf = −25 dBm and a sensitivity ε of 300 mV/mW. The rectified signal shows a strong dependence on MTJ dimensions: it increases by a factor of 5–6 when reducing the diameter from 180 to 50 nm. Furthermore, this enhancement can be doubled when reducing the free layer thickness from 1.8 to 1.6 nm. This size-related enhancement is attributed to several jointly acting effects: the amplitude of the spin transfer torque that depends inversely on the diameter, the effective anisotropy that depends on the thickness of the excited layer, and the tunneling magneto-resistance ratio that for the devices studied here depends on diameter. The obtained results indicate that the geometry of the MTJ can be used to design spintronic based rf detectors with optimized sensitivity.

  • M. Trassin, V. Garcia, Bringing some bulk into ferroelectric devices. Nature Materials. 21, 730 (2022).
    Résumé : Sub-100-mV switching at the nanosecond timescale is achieved in ferroelectric devices by approaching bulk-like perfection in prototypical BaTiO3 thin films.

  • F. Trier, P. Noël, J. - V. Kim, J. - P. Attané, L. Vila, M. Bibes, Oxide spin-orbitronics: spin–charge interconversion and topological spin textures. Nature Reviews Materials. 7, 258 (2022).
    Résumé : Spin–orbit coupling can be leveraged to enable new functional properties in oxide materials, in particular, for spintronics applications. This Review surveys significant recent advances in the field of oxide spin-orbitronics and discusses its future perspectives.

  • S. Varotto, A. Johansson, B. Göbel, L. Moreno Vicente-Arche, S. Mallik, J. Bréhin, R. Salazar, F. Bertran, P. le Fèvre, N. Bergeal, J. Rault, I. Mertig, M. Bibes, Direct visualization of Rashba-split bands and spin/orbital-charge interconversion at KTaO3 interfaces. Nature Communications. 13, 6165 (2022).
    Résumé : Visualization of the Rashbasplit bands in oxide two-dimensional electron gases is lacking, which hampers understanding of their rich spin-orbit physics. Here, the authors investigate KTaO3 two dimensional electron gases and their Rashba-split bands.

  • Q. H. Wang, A. Bedoya-Pinto, M. Blei, A. H. Dismukes, A. Hamo, S. Jenkins, M. Koperski, Y. Liu, Q. - C. Sun, E. J. Telford, H. H. Kim, M. Augustin, U. Vool, J. - X. Yin, L. H. Li, A. Falin, C. R. Dean, F. Casanova, R. F. L. Evans, M. Chshiev, A. Mishchenko, C. Petrovic, R. He, L. Zhao, A. W. Tsen, B. D. Gerardot, M. Brotons-Gisbert, Z. Guguchia, X. Roy, S. Tongay, Z. Wang, M. Z. Hasan, J. Wrachtrup, A. Yacoby, A. Fert, S. Parkin, K. S. Novoselov, P. Dai, L. Balicas, E. J. G. Santos, The Magnetic Genome of Two-Dimensional van der Waals Materials. ACS Nano. 16, 6960 (2022).
    Résumé : Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the brief time after their discovery, 2D magnets have blossomed into a rich area for investigation, where fundamental concepts in magnetism are challenged by the behavior of spins that can develop at the single layer limit. However, much effort is still needed in multiple fronts before 2D magnets can be routinely used for practical implementations. In this comprehensive review, prominent authors with expertise in complementary fields of 2D magnetism (i.e., synthesis, device engineering, magneto-optics, imaging, transport, mechanics, spin excitations, and theory and simulations) have joined together to provide a genome of current knowledge and a guideline for future developments in 2D magnetic materials research.

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