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935 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I10-Beamline for Advanced Dichroism	X-ray detected ferromagnetic resonance techniques for the study of magnetization dynamics Gerrit Van Der Laan , Thorsten Hesjedal Nuclear Instruments And Methods In Physics Research Section B: Beam Interactions With Materials And Atoms 540, 85 - 93 DOI: 10.1016/j.nimb.2023.04.005 Open Access Show Abstract ▼ Abstract: Element-specific spectroscopies using synchrotron-radiation can provide unique insights into materials properties. The recently developed technique of X-ray detected ferromagnetic resonance (XFMR) allows studying the magnetization dynamics of magnetic spin structures. Magnetic sensitivity in XFMR is obtained from the X-ray magnetic circular dichroism (XMCD) effect, where the phase of the magnetization precession of each magnetic layer with respect to the exciting radio frequency is obtained using stroboscopic probing of the spin precession. Measurement of both amplitude and phase response in the magnetic layers as a function of bias field can give a clear signature of spin-transfer torque (STT) coupling between ferromagnetic layers due to spin pumping. In the last few years, there have been new developments utilizing X-ray scattering techniques to reveal the precessional magnetization dynamics of ordered spin structures in the GHz frequency range. The techniques of diffraction and reflectometry ferromagnetic resonance (DFMR and RFMR) provide novel ways for the probing of the dynamics of chiral and multilayered magnetic materials, thereby accessing key information relevant to the engineering and development of high-density and low-energy consumption data processing solutions.	Jul 2023
I10-Beamline for Advanced Dichroism	Evolution of emergent monopoles into magnetic skyrmion strings Haonan Jin , Wancong Tan , Yizhou Liu , Kejing Ran , Raymond Fan , Yanyan Shangguan , Yao Guang , Gerrit Van Der Laan , Thorsten Hesjedal , Jinsheng Wen , Guoqiang Yu , Shilei Zhang Nano Letters DOI: 10.1021/acs.nanolett.3c01117 Diamond Proposal Number(s): [27692, 28933, 30749] Open Access Show Abstract ▼ Abstract: Topological defects are fundamental concepts in physics, but little is known about the transition between distinct types across different dimensionalities. In topological magnetism, as in field theory, the transition between 1D strings and 0D monopoles is a key process whose observation has remained elusive. Here, we introduce a novel mechanism that allows for the controlled stabilization of emergent monopoles and show that magnetic skyrmion strings can be folded into monopoles. Conversely, they act as seeds out of which the entire string structure can unfold, containing its complete information. In chiral magnets, this process can be observed by resonant elastic X-ray scattering when the objects are in proximity to a polarized ferromagnet, whereby a pure monopole lattice is emerging on the surface. Our experimental proof of the reversible evolution from monopole to string sheds new light on topological defects and establishes the emergent monopole lattice as a new 3D topological phase.	Jun 2023
E02-JEM ARM 300CF	Nanoscale LiZnN - luminescent half-heusler quantum dots S. Carter-Searjeant , S. M. Fairclough , S. J. Haigh , Y. Zou , R. J. Curry , P. N. Taylor , C. Huang , R. Fleck , P. Machado , A. I. Kirkland , M. A. Green Acs Applied Optical Materials 1 DOI: 10.1021/acsaom.3c00065 Diamond Proposal Number(s): [16892, 17837] Open Access Show Abstract ▼ Abstract: Colloidal semiconductor quantum dots are a well-established technology, with numerous materials available either commercially or through the vast body of literature. The prevalent materials are cadmium-based and are unlikely to find general acceptance in most applications. While the III–V family of materials is a likely substitute, issues remain about its long-term suitability, and other earth-abundant materials are being explored. In this report, we highlight a nanoscale half-Heusler semiconductor, LiZnN, composed of readily available elements as a potential alternative system to luminescent II–VI and III–V nanoparticle quantum dots.	Jun 2023
I06-Nanoscience	Antiferromagnetic half-skyrmions electrically generated and controlled at room temperature O. J. Amin , S. F. Poole , S. Reimers , L. X. Barton , A. Dal Din , F. Maccherozzi , S. S. Dhesi , V. Novák , F. Krizek , J. S. Chauhan , R. P. Campion , A. W. Rushforth , T. Jungwirth , O. A. Tretiakov , K. W. Edmonds , P. Wadley Nature Nanotechnology 6 DOI: 10.1038/s41565-023-01386-3 Diamond Proposal Number(s): [26255, 27845] Open Access Show Abstract ▼ Abstract: Topologically protected magnetic textures are promising candidates for information carriers in future memory devices, as they can be efficiently propelled at very high velocities using current-induced spin torques. These textures—nanoscale whirls in the magnetic order—include skyrmions, half-skyrmions (merons) and their antiparticles. Antiferromagnets have been shown to host versions of these textures that have high potential for terahertz dynamics, deflection-free motion and improved size scaling due to the absence of stray field. Here we show that topological spin textures, merons and antimerons, can be generated at room temperature and reversibly moved using electrical pulses in thin-film CuMnAs, a semimetallic antiferromagnet that is a testbed system for spintronic applications. The merons and antimerons are localized on 180° domain walls, and move in the direction of the current pulses. The electrical generation and manipulation of antiferromagnetic merons is a crucial step towards realizing the full potential of antiferromagnetic thin films as active components in high-density, high-speed magnetic memory devices.	May 2023
I15-Extreme Conditions	Acceptor doping and actuation mechanisms in Sr-doped BiFeO3BaTiO3 ceramics Ziqi Yang , Yizhe Li , Bing Wang , Juncheng Pan , Annette K. Kleppe , David Hall Journal Of Materiomics 71 DOI: 10.1016/j.jmat.2023.04.007 Diamond Proposal Number(s): [30553] Open Access Show Abstract ▼ Abstract: BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0 at%, on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3 at %) yielded enhanced ferroelectric (Pmax ~ 0.37 C m-2, Pr ~ 0.30 C m-2) and piezoelectric (d33 ~ 178 pC N-1, kp ~ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.	May 2023
I06-Nanoscience	Identifying the domain-wall spin structure in antiferromagnetic NiO/Pt C. Schmitt , L. Sanchez-Tejerina , M. Filianina , F. Fuhrmann , H. Meer , R. Ramos , F. Maccherozzi , D. Backes , E. Saitoh , G. Finocchio , L. Baldrati , M. Klaui Physical Review B 107 DOI: 10.1103/PhysRevB.107.184417 Diamond Proposal Number(s): [22448] Show Abstract ▼ Abstract: The understanding of antiferromagnetic domain walls, which are the interface between domains with different Néel order orientations, is a crucial aspect to enable the use of antiferromagnetic materials as active elements in future spintronic devices. In this work, we demonstrate that in antiferromagnetic NiO/Pt bilayers arbitrary-shaped structures can be generated by switching driven by electrical current pulses. The generated domains are T domains, separated from each other by a domain wall whose spins are pointing toward the average direction of the two T domains rather than the common axis of the two planes. Interestingly, this direction is the same for the whole domain wall indicating the absence of strong Lifshitz invariants. The domain wall can be micromagnetically modeled by strain distributions in the NiO thin film induced by the MgO substrate, deviating from the bulk anisotropy. From our measurements we determine the domain-wall width to have a full width at half maximum of Δ = 98 ± 10 nm, demonstrating strong confinement.	May 2023
I05-ARPES	Experimental electronic structure of the electrically switchable antiferromagnet CuMnAs A. Garrison Linn , Peipei Hao , Kyle N. Gordon , Dushyant Narayan , Bryan S. Berggren , Nathaniel Speiser , Sonka Reimers , Richard P. Campion , Vít Novák , Sarnjeet S. Dhesi , Timur K. Kim , Cephise Cacho , Libor Šmejkal , Tomáš Jungwirth , Jonathan D. Denlinger , Peter Wadley , Daniel S. Dessau Npj Quantum Materials 8 DOI: 10.1038/s41535-023-00554-x Diamond Proposal Number(s): [24224] Open Access Show Abstract ▼ Abstract: Tetragonal CuMnAs is a room temperature antiferromagnet with an electrically reorientable Néel vector and a Dirac semimetal candidate. Direct measurements of the electronic structure of single-crystalline thin films of tetragonal CuMnAs using angle-resolved photoemission spectroscopy (ARPES) are reported, including Fermi surfaces (FS) and energy-wavevector dispersions. After correcting for a chemical potential shift of ≈− 390 meV (hole doping), there is excellent agreement of FS, orbital character of bands, and Fermi velocities between the experiment and density functional theory calculations. In addition, 2×1 surface reconstructions are found in the low energy electron diffraction (LEED) and ARPES. This work underscores the need to control the chemical potential in tetragonal CuMnAs to enable the exploration and exploitation of the Dirac fermions with tunable masses, which are predicted to be above the chemical potential in the present samples.	May 2023
I05-ARPES	Temperature-dependent electronic structure measurements of CrSBr James E. Nunn , Matthew D. Watson , Laxman Nagi-Reddy , Cephise Cacho , Neil R. Wilson Graphene2023 Show Abstract ▼ Abstract: In recent years, chromium sulphur bromide (CrSBr) has emerged as a promising highly- anisotropic semiconducting two-dimensional (2D) magnetic material to explore spintronics and quantum transport due to its strongly correlated quasiparticle interactions [1]. CrSBr is an A-type layered antiferromagnet; in the bulk material, above the Néel temperature (TN = 132K) it transitions to an intermediate ferromagnetic phase before becoming paramagnetic at high temperature. Experimental work on its fascinating optoelectronic properties has been heavily supported by electronic structure calculations using a variety of methods [2,3], but direct band structure measurements to test these predictions are still lacking. Recent angle- resolved photoemission microscopy (ARPES) measurements of bulk CrSBr were unable to measure below TN due to charging effects [4]. Here, we overcome this limitation through exfoliation of CrSBr flakes onto a template-stripped gold surface (Figure 1a) [5]. Using the nanoARPES endstation of the i05 beamline at Diamond Light Source, ARPES was acquired without charging from thin flakes (~10 nm thick) at temperatures down to < 40 K. Photon energy, and polarisation, dependent measurements confirm a strongly 2D dispersion and link the band dispersions to different atomic orbitals. Temperature-dependent measurements highlight electronic structure changes through the magnetic phase transitions, including shifts of the low energy valence bands and band splitting suggestive of spin-ordering (Figure 1b,c). These results also demonstrate a simple approach for the measurement of the low- temperature band structure of insulating layered materials.	May 2023
	Narrowband, angle-tunable, helicity-dependent terahertz emission from nanowires of the topological dirac semimetal Cd3As2 Jessica L. Boland , Djamshid A. Damry , Chelsea Q. Xia , Piet Schoenherr , Dharmalingam Prabhakaran , Laura M. Herz , Thorsten Hesjedal , Michael B. Johnston Acs Photonics 59 DOI: 10.1021/acsphotonics.3c00068 Open Access Show Abstract ▼ Abstract: All-optical control of terahertz pulses is essential for the development of optoelectronic devices for next-generation quantum technologies. Despite substantial research in THz generation methods, polarization control remains difficult. Here, we demonstrate that by exploiting band structure topology, both helicity-dependent and helicity-independent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. We show that narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarization. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21–1.40 THz as the angle is tuned from 15 to 45°. We therefore present Cd3As2 nanowires as a promising novel material platform for controllable terahertz emission.	Apr 2023
I06-Nanoscience	Current-driven writing process in antiferromagnetic Mn2Au for memory applications S. Reimers , Y. Lytvynenko , Y. R. Niu , E. Golias , B. Sarpi , L. S. I. Veiga , T. Denneulin , A. Kovács , R. E. Dunin-Borkowski , J. Bläßer , M. Klaui , M. Jourdan Nature Communications 14 DOI: 10.1038/s41467-023-37569-8 Diamond Proposal Number(s): [30141] Open Access Show Abstract ▼ Abstract: Current pulse driven Néel vector rotation in metallic antiferromagnets is one of the most promising concepts in antiferromagnetic spintronics. We show microscopically that the Néel vector of epitaxial thin films of the prototypical compound Mn2Au can be reoriented reversibly in the complete area of cross shaped device structures using single current pulses. The resulting domain pattern with aligned staggered magnetization is long term stable enabling memory applications. We achieve this switching with low heating of ≈20 K, which is promising regarding fast and efficient devices without the need for thermal activation. Current polarity dependent reversible domain wall motion demonstrates a Néel spin-orbit torque acting on the domain walls.	Apr 2023

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