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299 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	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
	Synchrotron radiation techniques and their application to actinide materials R. Caciuffo , G. H. Lander , G. Van Der Laan Reviews Of Modern Physics 95 DOI: 10.1103/RevModPhys.95.015001 Show Abstract ▼ Abstract: Research on actinide materials, both basic and applied, has been greatly advanced by the general techniques available from high-intensity photon beams from x-ray synchrotron sources. The most important single reason is that such x-ray sources can work with minute (e.g., microgram) samples, and at this level the radioactive hazards of actinides are significantly reduced. The form and encapsulation procedures used for different techniques are discussed, followed by the basic theory for interpreting the results. To demonstrate the potential of synchrotron radiation techniques for the study of lattice and electronic structure, hybridization effects, multipolar order, and lattice dynamics in actinide materials, a selection of x-ray diffraction, resonant elastic x-ray scattering, x-ray magnetic circular dichroism, resonant and nonresonant inelastic scattering, dispersive inelastic x-ray scattering, and conventional and resonant photoemission experiments are reviewed.	Mar 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
I21-Resonant Inelastic X-ray Scattering (RIXS)	Resonant inelastic x-ray scattering from U3O8 and UN Eleanor Lawrence Bright , Lei Xu , Lottie Harding , Ross Springell , Andrew Walters , Martin Sundermann , Mirian Garcia-Fernandez , Stefano Agrestini , Roberto Caciuffo , Gerrit Van Der Laan , Gerry H. Lander Journal Of Physics: Condensed Matter DOI: 10.1088/1361-648X/acb8f4 Diamond Proposal Number(s): [29274] Show Abstract ▼ Abstract: Resonant inelastic x-ray scattering (RIXS) using an incident energy tuned to the uranium N4,5 absorption edges is reported from epitaxial films of α-U3O8 and UN. Theory shows that for U3O8 the multiplets associated with a 5f1 configuration with a ground state of 2F5/2 and the excited state of 2F7/2 are observed. However, the strong transition predicted at a transfer energy of 1.67 eV is not observed. We assume this is a consequence of the intermediate state lifetime broadening due to interaction with continuum states when the transferred energy exceeds the onset of the continuum in the presence of the core hole. This hypothesis is supported by the results obtained for the 5f-itinerant system UN, where no sharp transitions have been observed, although the broad scattering response centered at ∼ 1 eV is considered a signature of a predominantly 5f3 configuration in this band-like semi-metallic system. These experiments and theory add important information on these materials, both of which have been investigated since the 1960s, as well as whether RIXS at the uranium N edge can become a valuable tool for actinide research.	Feb 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
I06-Nanoscience	Elucidation of orbital moment, anisotropy, and magnetic damping in epitaxial Fe3O4 films C. Love , J. E. Beevers , B. Achinuq , R. Fan , K. Matsuzaki , T. Susaki , V. K. Lazarov , S. S. Dhesi , G. Van Der Laan , S. A. Cavill Physical Review B 107 DOI: 10.1103/PhysRevB.107.064414 Diamond Proposal Number(s): [14135] Show Abstract ▼ Abstract: The size of the orbital moment in Fe 3 O 4 has been the subject of a long-standing and contentious debate. In this paper, we make use of ferromagnetic resonance (FMR) spectroscopy and x-ray magnetic circular dichroism (XMCD) to provide complementary determinations of the size of the orbital moment in “bulklike” epitaxial Fe 3 O 4 films grown on yttria-stabilized zirconia (111) substrates. Annealing the 100 nm as-grown films to 1100 ∘ C in a reducing atmosphere improves the stoichiometry and microstructure of the films, allowing for bulklike properties to be recovered as evidenced by x-ray diffraction and vibrating sample magnetometry. In addition, in-plane angular FMR spectra exhibit a crossover from a fourfold symmetry to the expected sixfold symmetry of the (111) surface, together with an anomalous peak in the FMR linewidth at ∼ 10 GHz; this is indicative of low Gilbert damping in combination with two-magnon scattering. For the bulklike annealed sample, a spectroscopic splitting factor g ≈ 2.18 is obtained using both FMR and XMCD techniques, providing evidence for the presence of a finite orbital moment in Fe 3 O 4 .	Feb 2023
I10-Beamline for Advanced Dichroism	Polarization analysis by means of individual soft x-ray absorption spectra of rare earths Gerrit Van Der Laan , Thorsten Hesjedal , Peter Bencok Physical Review B 106 DOI: 10.1103/PhysRevB.106.214423 Diamond Proposal Number(s): [10207] Open Access Show Abstract ▼ Abstract: X-ray magnetic circular dichroism (XMCD), which by virtue of the sum rules provides element-specific spin and orbital moments, is obtained from the difference between two polarized spectra by reversing the direction of either the light helicity or the applied magnetic field. Usually, it is tacitly assumed that these two spectra are obtained using the same absolute degree of light and magnetic polarization. This is, however, not always possible and depends on circumstances that can be beyond control. First, we recapitulate the conventional XMCD sum rule method to obtain the values of the moments and emphasize some of the complications in the case of the rare-earth M 4 , 5 edges, such as the presence of strong core-hole j j overlap, linear dichroism, and magnetic dipole term ⟨ T z ⟩ . Instead, we propose an alternative method. Using the individual polarized x-ray absorption spectra obtained at the Ho and Dy M 5 edges, where each of the Δ J = − 1 , 0 , and + 1 transitions are separated by ∼ 2 eV in photon energy, we are able to determine independently the degree of circular dichroism in a single spectrum. Since light is a transverse wave, we need to include, apart from the circular dichroism, also a linear dichroism contribution in order to fit the circularly polarized spectra. In the measurements on paramagnetic rare-earth dopants it was found that reversing the field produces the same degree of circular dichroism, while reversing the helicity yields a ∼ 20% difference in the degree of circular dichroism.	Dec 2022

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