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Instruments / Technical Area	Publication Details	Published
I06-Nanoscience	Identification of Néel vector orientation in antiferromagnetic domains switched by currents in NiO/Pt thin films C. Schmitt , L. Baldrati , L. Sanchez-Tejerina , F. Schreiber , A. Ross , M. Filianina , S. Ding , F. Fuhrmann , R. Ramos , F. Maccherozzi , D. Backes , M.-A. Mawass , F. Kronast , S. Valencia , E. Saitoh , G. Finocchio , M. Klaui Physical Review Applied 15 DOI: 10.1103/PhysRevApplied.15.034047 Diamond Proposal Number(s): [22448] Show Abstract ▼ Abstract: Understanding the electrical manipulation of the antiferromagnetic order is a crucial aspect to enable the design of antiferromagnetic devices working at THz frequencies. Focusing on collinear insulating antiferromagnetic Ni O / Pt thin films as a materials platform, we identify the crystallographic orientation of the domains that can be switched by currents and quantify the Néel-vector direction changes. We demonstrate electrical switching between different T domains by current pulses, finding that the Néel-vector orientation in these domains is along [ ± 5 ± 5 19], different compared to the bulk ⟨ 112 ⟩ directions. The final state of the in-plane component of the Néel vector n IP after switching by current pulses j along the [ 1 ± 1 0 ] directions is n IP ∥ j . By comparing the observed Néel-vector orientation and the strain in the thin films, assuming that this variation arises solely from magnetoelastic effects, we quantify the order of magnitude of the magnetoelastic coupling coefficient as b 0 + 2 b 1 = 3 × 10 7 J / m 3 . This information is key for the understanding of current-induced switching in antiferromagnets and for the design and use of such devices as active elements in spintronic devices.	Mar 2021
I06-Nanoscience	Electrical detection of the spin reorientation transition in antiferromagnetic TmFeO3 thin films by spin Hall magnetoresistance S. Becker , A. Ross , R. Lebrun , L. Baldrati , S. Ding , F. Schreiber , F. Maccherozzi , D. Backes , M. Klaui , G. Jakob Physical Review B 103 DOI: 10.1103/PhysRevB.103.024423 Diamond Proposal Number(s): [23819] Show Abstract ▼ Abstract: Tm Fe O 3 (TFO) is a canted antiferromagnet that undergoes a spin reorientation transition (SRT) with temperature between 82 and 94 K in single crystals. In this temperature region, the Néel vector continuously rotates from the crystallographic c axis (below 82 K) to the a axis (above 94 K). The SRT allows for a temperature control of distinct antiferromagnetic states without the need for a magnetic field, making it apt for applications working at terahertz frequencies. For device applications, thin films of TFO are required as well as an electrical technique for read-out of the magnetic state. Here, we demonstrate that orthorhombic TFO thin films can be grown by pulsed laser deposition and the detection of the SRT in TFO thin films can be accessed by making use of the all-electrical spin Hall magnetoresistance, in good agreement for the temperature range where the SRT occurs in bulk crystals. Our results demonstrate that one can electrically detect the SRT in insulators.	Jan 2021
I06-Nanoscience	An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit Andrew Ross , Romain Lebrun , Lorenzo Baldrati , Akashdeep Kamra , Olena Gomonay , Shilei Ding , Felix Schreiber , Dirk Backes , Francesco Maccherozzi , Daniel A. Grave , Avner Rothschild , Jairo Sinova , Mathias Klaui Applied Physics Letters 117 DOI: 10.1063/5.0032940 Diamond Proposal Number(s): [23819] Show Abstract ▼ Abstract: We report room-temperature long-distance spin transport of magnons in antiferromagnetic thin-film hematite doped with Zn. The additional dopants significantly alter the magnetic anisotropies, resulting in a complex equilibrium spin structure that is capable of efficiently transporting spin angular momentum at room temperature without the need for a well-defined, pure easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion lengths of up to 1.5 μm, and magnetic domain governed decay lengths of 175 nm for the low-frequency magnons, through electrical transport measurements demonstrating that the introduction of nonmagnetic dopants does not strongly reduce the transport length scale, showing that the magnetic damping of hematite is not significantly increased. We observe a complex field dependence of the nonlocal signal independent of the magnetic state visible, in the local magnetoresistance and direct magnetic imaging of the antiferromagnetic domain structure. We explain our results in terms of a varying and applied field-dependent ellipticity of the magnon modes reaching the detector electrode allowing us to tune the spin transport.	Dec 2020
I06-Nanoscience	Imaging of current induced Néel vector switching in antiferromagnetic Mn 2 Au S. Yu. Bodnar , M. Filianina , S. P. Bommanaboyena , T. Forrest , F. Maccherozzi , A. A. Sapozhnik , Y. Skourski , M. Klaui , M. Jourdan Physical Review B 99 DOI: 10.1103/PhysRevB.99.140409 Diamond Proposal Number(s): [20534] Show Abstract ▼ Abstract: The effects of current induced Néel spin-orbit torques on the antiferromagnetic domain structure of epitaxial Mn2Au thin films were investigated by x-ray magnetic linear dichroism–photoemission electron microscopy.We observed current induced switching of antiferromagnetic domains essentially corresponding to morphological features of the samples. Reversible as well as irreversible Néel vector reorientation was obtained in different parts of the samples and the switching of up to 30% of all domains in the field of view of 10 μm is demonstrated. Our direct microscopical observations are compared to and fully consistent with anisotropic magnetoresistance effects previously attributed to current induced Néel vector switching in Mn2Au.	Apr 2019
I06-Nanoscience	Direct imaging of antiferromagnetic domains in Mn 2 Au manipulated by high magnetic fields A. A. Sapozhnik , M. Filianina , S. Yu. Bodnar , A. Lamirand , M.-a. Mawass , Y. Skourski , H.-j. Elmers , H. Zabel , M. Klaui , M. Jourdan Physical Review B 97, 134429 DOI: 10.1103/PhysRevB.97.134429 Diamond Proposal Number(s): [17120] Show Abstract ▼ Abstract: In the field of antiferromagnetic (AFM) spintronics, information about the Néel vector, AFM domain sizes, and spin-flop fields is a prerequisite for device applications but is not available easily.We have investigated AFM domains and spin-flop-induced changes of domain patterns in Mn2Au(001) epitaxial thin films by x-ray magnetic linear dichroism photoemission electron microscopy (PEEM) using magnetic fields up to 70 T. As-prepared Mn2Au films exhibit AFM domains with an average size of 1μm. Application of a 30 T field, exceeding the spin-flop field, along a magnetocrystalline easy axis dramatically increases the AFM domain size with Néel vectors perpendicular to the applied field direction. The width of Néel-type domain walls (DW) is below the spatial resolution of the PEEM and therefore can only be estimated from an analysis of the DW profile to be smaller than 80 nm. Furthermore, using the values for the DW width and the spin-flop field, we evaluate an in-plane anisotropy constant ranging between 1 and 17 eV/f.u..	Apr 2018
NONE-No attached Diamond beamline	Role of B diffusion in the interfacial Dzyaloshinskii-Moriya interaction in Ta/Co20Fe60B20/MgO nanowires R. Lo Conte , E. Martinez , A. Hrabec , A. Lamperti , T. Schulz , L. Nasi , L. Lazzarini , R. Mantovan , F. Maccherozzi , S. Dhesi , B. Ocker , Christopher Marrows , Thomas Moore , Mathias Klaui Physical Review B 91 (1) DOI: 10.1103/PhysRevB.91.014433 Show Abstract ▼ Abstract: We report on current-induced domain wall motion in Ta/Co20Fe60B20/MgO nanowires. Domain walls are observed to move against the electron flow when no magnetic field is applied, while a field along the nanowires strongly affects the domain wall motion velocity. A symmetric effect is observed for up-down and down-up domain walls. This indicates the presence of right-handed domain walls, due to a Dzyaloshinskii-Moriya interaction (DMI) with a DMI coefficient D=+0.06mJ/m2. The positive DMI coefficient is interpreted to be a consequence of B diffusion into the Ta buffer layer during annealing, which was observed by chemical depth profiling measurements. The experimental results are compared to one-dimensional model simulations including the effects of pinning. This modeling allows us to reproduce the experimental outcomes and reliably extract a spin-Hall angle θSH=0.11 for Ta in the nanowires, showing the importance of an analysis that goes beyond the model for perfect nanowires.	Jan 2015
I06-Nanoscience	Magnetic-field-induced domain-wall motion in permalloy nanowires with modified Gilbert damping Thomas Moore , Phillipe Mohrke , Lutz Heyne , Andreas Kaldun , Mathias Kläui , Dirk Backes , Jan Rhensius , Laura Heyderman , Jan-ulrich Thiele , Georg Woltersdorf , Arantxa Rodriguez , Frithjof Nolting , Tevfik Mentes , Miguel Nino , Andrea Locatelli , Alessandro Potenza , Helder Marchetto , Stuart Cavill , Sarnjeet Dhesi Physical Review B 82 (9) DOI: 10.1103/PhysRevB.82.094445 Show Abstract ▼ Abstract: Domain wall (DW) depinning and motion in the viscous regime induced by magnetic fields, are investigated in planar permalloy nanowires in which the Gilbert damping is tuned in the range 0.008–0.26 by doping with Ho. Real time, spatially resolved magneto-optic Kerr effect measurements yield depinning field distributions and DW mobilities. Depinning occurs at discrete values of the field which are correlated with different metastable DW states and changed by the doping. For α<0.033, the DW mobilities are smaller than expected while for α>=0.033, there is agreement between the measured DW mobilities and those predicted by the standard one-dimensional model of field-induced DW motion. Micromagnetic simulations indicate that this is because as increases, the DW spin structure becomes increasingly rigid. Only when the damping is large can he DW be approximated as a pointlike quasiparticle that exhibits the simple translational motion predicted in the viscous regime. When the damping is small, the DW spin structure undergoes periodic distortions that lead to a velocity reduction. We therefore show that Ho doping of permalloy nanowires enables engineering of the DW depinning and mobility, as well as the extent of the viscous regime.	Sep 2010
I06-Nanoscience	Scaling of spin relaxation and angular momentum dissipation in permalloy nanowires T. Moore , M. Klaui , L. Heyne , P. Mohrke , D. Backes , J. Rhensius , U. Rudiger , L. Heyderman , J.-u. Thiele , G. Wolterstorf , C. Back , A. Fraile Rodriquez , F. Nolting , T. Mentes , M. Nino , A. Locatelli , S. Dhesi , S. Cavill , H. Marchetto , A. Potenza Physical Review B 80 (13), 132403 DOI: 10.1103/PhysRevB.80.132403 Show Abstract ▼ Abstract: We study the relationship between the damping (alpha) and the nonadiabaticity of the spin transport (beta) in permalloy nanowires. alpha is engineered by Ho doping, and from the characteristics of the current-induced domain-wall velocity, determined by high-resolution x-ray magnetic circular-dichroism photoemission electron microscopy, beta due to spin relaxation is measured. We find that beta scales with alpha and conclude that the spin relaxation that leads to nonadiabatic spin torque originates from the same underlying mechanism as the angular momentum dissipation that causes viscous damping.	Oct 2009
I06-Nanoscience	Domain wall velocity measurement in permalloy nanowires with X-ray magnetic circular dichroism imaging and single shot Kerr microscopy T. A. Moore , M. Klaui , L. Heyne , P. Möhrke , D. Backes , J. Rhensius , U. Rüdiger , L. J. Heyderman , T. O. Mentes , M. A. Niño , A. Locatelli , A. Potenza , S. S. Dhesi , S. Cavill , H. Marchetto Journal Of Magnetism And Magnetic Materials DOI: 10.1016/j.jmmm.2009.06.048 Show Abstract ▼ Abstract: Domain walls (DWs) propagated along nanoscale magnetic wires by current or field pulses could potentially be used for data storage or logic applications, but the understanding of the DW dynamics, particularly under the influence of spin-polarized current, is incomplete. Measuring the velocity can give insights into the physics of the DW motion. Here we demonstrate DW velocity measurements in permalloy (Ni80Fe20Ni80Fe20) nanowires (1500 nm width and 20 nm thickness) using the techniques of X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) to image the magnetic contrast in the nanowires, and single shot Kerr microscopy, which allows for dynamic measurements. The magnetic imaging yields the average velocity as well as information on the DW spin structure, whereas the single shot method highlights the stochastic nature of the DW motion.	Jun 2009

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