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110 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
	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
I10-Beamline for Advanced Dichroism	Observation of the chiral soliton lattice above room temperature R. Brearton , S. H. Moody , L. A. Turnbull , P. D. Hatton , A. Štefančič , G. Balakrishnan , G. Van Der Laan , T. Hesjedal Advanced Physics Research 2 DOI: 10.1002/apxr.202200116 Diamond Proposal Number(s): [30613] Open Access Show Abstract ▼ Abstract: Magnetic chiral soliton lattices (CSLs) emerge from the helical phase in chiral magnets when magnetic fields are applied perpendicular to the helical propagation vector, and they show great promise for next-generation magnetic memory applications. These one-dimensional structures are previously observed at low temperatures in samples with uniaxial symmetry. Here, it is found that in-plane fields are the key to stabilizing the CSL in cubic Co8Zn10Mn2 over the entire temperature range from 15 K to below the Curie temperature (365 K). Using small-angle resonant elastic X-ray scattering, it is observed that the CSL is stabilized with an arbitrary in-plane propagation vector, while its thin plate geometry plays a deciding role in the soliton wavelength as a function of applied field. This work paves the way for high temperature, real world applications of soliton physics in future magnetic memory devices.	Apr 2023
E02-JEM ARM 300CF	Controlling in‐plane magnetic anisotropy of Co films on MgO substrates using glancing angle deposition Andreas Frisk , Barat Achinuq , David G. Newman , Emily Heppell , Maciej Dabrowski , Robert J. Hicken , Gerrit Van Der Laan , Thorsten Hesjedal Physica Status Solidi (a) DOI: 10.1002/pssa.202300010 Diamond Proposal Number(s): [23285] Show Abstract ▼ Abstract: The ability to control the in-plane magnetic anisotropy of a thin film is important for magnetic device applications. One way of accomplishing this task is by glancing angle deposition (GLAD). In this study, thin Co layers have been deposited using GLAD magnetron sputtering on MgO(001) and MgO(110) substrates. For Co films on MgO(001), the in-plane anisotropy direction can be directly controlled via the deposition angle. In contrast, for Co on MgO(110), the anisotropy due to the deposition angle is competing with the anisotropy induced by the substrate, while the growth parameters determine which contribution dominates. On the other hand, while on MgO(001) the deposition angle as well as the film thickness affect the strength of the Co in-plane anisotropy, no influence of these parameters on the magnetic properties is found for films on MgO(110).	Mar 2023
I10-Beamline for Advanced Dichroism	Spin pumping through nanocrystalline topological insulators David M. Burn , Jheng-Cyuan Lin , Ryuji Fujita , Barat Achinuq , Joshua Bibby , Angadjit Singh , Andreas Frisk , Gerrit Van Der Laan , Thorsten Hesjedal Nanotechnology DOI: 10.1088/1361-6528/acc663 Diamond Proposal Number(s): [21872, 27487] Open Access Show Abstract ▼ Abstract: The topological surface states (TSSs) in topological insulators (TIs) offer exciting prospects for dissipationless spin transport. Common spin-based devices, such as spin valves, rely on trilayer structures in which a non-magnetic (NM) layer is sandwiched between two ferromagnetic (FM) layers. The major disadvantage of using high-quality single-crystalline TI films in this context is that a single pair of spin-momentum locked channels spans across the entire film, meaning that only a very small spin current can be pumped from one FM to the other, along the side walls of the film. On the other hand, using nanocrystalline TI films, in which the grains are large enough to avoid hybridization of the TSSs, will effectively increase the number of spin channels available for spin pumping. Here, we used an element-selective, x-ray based ferromagnetic resonance technique to demonstrate spin pumping from a FM layer at resonance through the TI layer and into the FM spin sink.	Mar 2023
I10-Beamline for Advanced Dichroism	Probing the local electronic structure in metal halide perovskites through cobalt substitution Amir A. Haghighirad , Matthew T. Klug , L. B. Duffy , Junjie Liu , Arzhang Ardavan , Gerrit Van Der Laan , Thorsten Hesjedal , Henry J. Snaith Small Methods 642 DOI: 10.1002/smtd.202300095 Diamond Proposal Number(s): [16141] Open Access Show Abstract ▼ Abstract: Owing to the unique chemical and electronic properties arising from 3d-electrons, substitution with transition metal ions is one of the key routes for engineering new functionalities into materials. While this approach has been used extensively in complex metal oxide perovskites, metal halide perovskites have largely resisted facile isovalent substitution. In this work, it is demonstrated that the substitution of Co2+ into the lattice of methylammonium lead triiodide imparts magnetic behavior to the material while maintaining photovoltaic performance at low concentrations. In addition to comprehensively characterizing its magnetic properties, the Co2+ ions themselves are utilized as probes to sense the local electronic environment of Pb in the perovskite, thereby revealing the nature of their incorporation into the material. A comprehensive understanding of the effect of transition metal incorporation is provided, thereby opening the substitution gateway for developing novel functional perovskite materials and devices for future technologies.	Mar 2023
I10-Beamline for Advanced Dichroism	Observation of the skyrmion side-face state in a chiral magnet Xiaodong Xie , Kejing Ran , Yizhou Liu , Raymond Fan , Wancong Tan , Haonan Jin , Manuel Valvidares , Nicolas Jaouen , Haifeng Du , Gerrit Van Der Laan , Thorsten Hesjedal , Shilei Zhang Physical Review B 107 DOI: 10.1103/PhysRevB.107.L060405 Diamond Proposal Number(s): [20437, 26148, 22629] Show Abstract ▼ Abstract: We identify a three-dimensional skyrmion side-face state in chiral magnets that consists of a thin layer of modulated surface spirals and an array of phase-locked skyrmion screws. Such chiral spin structures lead to a characteristic X-shaped magnetic diffraction pattern in resonant elastic x-ray scattering, reminiscent of Photo 51 of the DNA double-helix diffraction. By measuring both thin plates and bulk Cu 2 OSeO 3 crystals in the field-in-plane geometry, we unambiguously identify the modulated skyrmion strings by retrieving their chirality and helix angle. The breaking of the translational symmetry along the side faces suppresses the bulk-favored conical state, providing a stabilization mechanism for the skyrmion lattice phase that has been overlooked so far.	Feb 2023
I10-Beamline for Advanced Dichroism	Tailoring the magnetic exchange interaction in MnBi2Te4 superlattices via the intercalation of ferromagnetic layers Peng Chen , Qi Yao , Junqi Xu , Qiang Sun , Alexander J. Grutter , Patrick Quarterman , Purnima P. Balakrishnan , Christy J. Kinane , Andrew J. Caruana , Sean Langridge , Ang Li , Barat Achinuq , Emily Heppell , Yuchen Ji , Shanshan Liu , Baoshan Cui , Jiuming Liu , Puyang Huang , Zhongkai Liu , Guoqiang Yu , Faxian Xiu , Thorsten Hesjedal , Jin Zou , Xiaodong Han , Haijun Zhang , Yumeng Yang , Xufeng Kou Nature Electronics 340 DOI: 10.1038/s41928-022-00880-1 Diamond Proposal Number(s): [30262] Show Abstract ▼ Abstract: The intrinsic magnetic topological insulator MnBi2Te4 (MBT) provides a platform for the creation of exotic quantum phenomena. Novel properties can be created by modification of the MnBi2Te4 framework, but the design of stable magnetic structures remains challenging. Here we report ferromagnet-intercalated MnBi2Te4 superlattices with tunable magnetic exchange interactions. Using molecular beam epitaxy, we intercalate ferromagnetic MnTe layers into MnBi2Te4 to create [(MBT)(MnTe)m]N superlattices and examine their magnetic interaction properties using polarized neutron reflectometry and magnetoresistance measurements. Incorporation of the ferromagnetic spacer tunes the antiferromagnetic interlayer coupling of the MnBi2Te4 layers through the exchange-spring effect at MnBi2Te4/MnTe hetero-interfaces. The MnTe thickness can be used to modulate the relative strengths of the ferromagnetic and antiferromagnetic order, and the superlattice periodicity can tailor the spin configurations of the synthesized multilayers.	Dec 2022
I10-Beamline for Advanced Dichroism	Three-dimensional structure of magnetic skyrmions R. Brearton , D. M. Burn , A. A. Haghighirad , G. Van Der Laan , T. Hesjedal Physical Review B 106 DOI: 10.1103/PhysRevB.106.214404 Diamond Proposal Number(s): [23784] Open Access Show Abstract ▼ Abstract: Magnetic skyrmions (skyrmions hereafter) are magnetization configurations, whose topological robustness and nanoscale size have led to speculation that they could find use as a next-generation information carrier. Skyrmions have been observed in magnetic multilayer materials that are thin compared to the radius of a skyrmion, and chiral cubic single crystals that can be far larger than any characteristic skyrmion scale. In these single crystals, one would expect that skyrmions could exhibit interesting three-dimensional (3D) characteristics. Here, the symmetry of the micromagnetic free energy is investigated. This symmetry permits a complex 3D modulation of a skyrmion string, which we show to be a requirement of a skyrmion coexisting with the conical state. We discuss the implications of this modulation with respect to Thiele's equation and interskyrmion interactions. Further to this internal modulation, we study theoretically and show experimentally that the strings themselves must contort towards the surfaces of their confining crystals.	Dec 2022

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