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31 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I10-Beamline for Advanced Dichroism - scattering I16-Materials and Magnetism	Role of the orbital moment in a series of isostructural weak ferromagnets D. Pincini , Federica Fabrizi , G. Beutier , G. Nisbet , H. Elnaggar , V. E. Dmitrienko , M. I. Katsnelson , Y. O. Kvashnin , A. I. Lichtenstein , V. V. Mazurenko , E. N. Ovchinnikova , O. V. Dimitrova , S. P. Collins Physical Review B 98 DOI: 10.1103/PhysRevB.98.104424 Diamond Proposal Number(s): [12479, 13608, 16227, 12478, 15987] Open Access Show Abstract ▼ Abstract: The orbital contribution to the magnetic moment of the transition-metal ion in the isostructural weak ferromagnets ACO3 (A= Mn,Co,Ni) and FeBO3 was investigated by a combination of first-principles calculations, nonresonant x-ray magnetic scattering, and x-ray magnetic circular dichroism. A nontrivial evolution of the orbital moment as a function of the 3d orbitals filling is revealed, with a particularly large value found in the Co member of the family. Here, the coupling between magnetic and lattice degrees of freedom produced by the spin-orbit interaction results in a large single-ion anisotropy and a peculiar magnetic-moment-induced electron cloud distortion, evidenced by the appearance of a subtle scattering amplitude at space-group-forbidden reflections and significant magnetostrictive effects. Our results, which complement a previous investigation on the sign of the Dzyaloshinskii-Moriya interaction across the series, highlight the importance of spin-orbit coupling in the physics of weak ferromagnets and prove the ability of modern first-principles calculations to predict the properties of materials where the Dzyaloshinskii-Moriya interaction is a fundamental ingredient of the magnetic Hamiltonian.	Sep 2018
I06-Nanoscience (XPEEM) I10-Beamline for Advanced Dichroism - scattering	Investigation of magnetic droplet solitons using x-ray holography with extended references E. Burgos-Parra , N. Bukin , S. Sani , A. I. Figueroa , G. Beutier , M. Dupraz , S. Chung , P. Dürrenfeld , Q. Tuan Le , S. M. Mohseni , A. Houshang , S. A. Cavill , R. J. Hicken , J. Akerman , G. Van Der Laan , F. Y. Ogrin Scientific Reports 8, 11533 DOI: 10.1038/s41598-018-29856-y Diamond Proposal Number(s): [15277] Open Access Show Abstract ▼ Abstract: A dissipative magnetic soliton, or magnetic droplet, is a structure that has been predicted to exist within a thin magnetic layer when non-linearity is balanced by dispersion, and a driving force counteracts the inherent damping of the spin precession. Such a soliton can be formed beneath a nano-contact (NC) that delivers a large spin-polarized current density into a magnetic layer with perpendicular magnetic anisotropy. Although the existence of droplets has been confirmed from electrical measurements and by micro-magnetic simulations, only a few attempts have been made to directly observe the magnetic landscape that sustains these structures, and then only for a restricted set of experimental parameter values. In this work we use and x-ray holography technique HERALDO, to image the magnetic structure of the [Co/Ni]x4 multilayer within a NC orthogonal pseudo spin-valve, for different range of magnetic fields and injected electric currents. The magnetic configuration imaged at −33 mA and 0.3 T for devices with 90 nm NC diameter reveals a structure that is within the range of current where the droplet soliton exist based on our electrical measurements and have it is consistent with the expected size of the droplet (∼100 nm diameter) and its spatial position within the sample. We also report the magnetisation configurations observed at lower DC currents in the presence of fields (0–50 mT), where it is expected to observe regimes of the unstable droplet formation.	Aug 2018
I16-Materials and Magnetism	Band filling control of the Dzyaloshinskii-Moriya interaction in weakly ferromagnetic insulators G. Beutier , S. P. Collins , O. v. Dimitrova , V. E. Dmitrienko , M. i. Katsnelson , Y. o. Kvashnin , A. i. Lichtenstein , V. v. Mazurenko , A. G. A. Nisbet , E. N. Ovchinnikova , D. Pincini Physical Review Letters 119 DOI: 10.1103/PhysRevLett.119.167201 Diamond Proposal Number(s): [7703, 11751] Open Access Show Abstract ▼ Abstract: We observe and explain theoretically a dramatic evolution of the Dzyaloshinskii-Moriya interaction (DMI) in the series of isostructural weak ferromagnets, MnCO3, FeBO3, CoCO3, and NiCO3. The sign of the interaction is encoded in the phase of the x-ray magnetic diffraction amplitude, observed through interference with resonant quadrupole scattering. We find very good quantitative agreement with first-principles electronic structure calculations, reproducing both sign and magnitude through the series, and propose a simplified “toy model” to explain the change in sign with 3d shell filling. The model gives insight into the evolution of the DMI in Mott and charge transfer insulators.	Oct 2017
	Time-resolved imaging of magnetic vortex dynamics using holography with extended reference autocorrelation by linear differential operator Nicholas Bukin , C. Mckeever , Erick Burgos-Parra , P. S. Keatley , R. J. Hicken , F. Y. Ogrin , G. Beutier , M. Dupraz , H. Popescu , N. Jaouen , F. Yakhou-Harris , Stuart Cavill , G. Van Der Laan Scientific Reports 6, 36307 DOI: 10.1038/srep36307 Open Access Show Abstract ▼ Abstract: The magnetisation dynamics of the vortex core and Landau pattern of magnetic thin-film elements has been studied using holography with extended reference autocorrelation by linear differential operator (HERALDO). Here we present the first time-resolved x-ray measurements using this technique and investigate the structure and dynamics of the domain walls after excitation with nanosecond pulsed magnetic fields. It is shown that the average magnetisation of the domain walls has a perpendicular component that can change dynamically depending on the parameters of the pulsed excitation. In particular, we demonstrate the formation of wave bullet-like excitations, which are generated in the domain walls and can propagate inside them during the cyclic motion of the vortex core. Based on numerical simulations we also show that, besides the core, there are four singularities formed at the corners of the pattern. The polarisation of these singularities has a direct relation to the vortex core, and can be switched dynamically by the wave bullets excited with a magnetic pulse of specific parameters. The subsequent dynamics of the Landau pattern is dependent on the particular configuration of the polarisations of the core and the singularities.	Oct 2016
	Holographic imaging of magnetization in a single layer nano-contact spin transfer oscillator Erick Omar Burgos Parra , Nicholas Bukin , Maxime Dupraz , Guillaume Beutier , Sohrab Redjai Sani , Horia Popescu , Stuart Cavill , Johan Akerman , Nicolas Jaouen , Paul Keatley , Robert Hicken , Gerrit Van Der Laan , Feodor Ogrin Ieee Transactions On Magnetics DOI: 10.1109/TMAG.2016.2528959 Show Abstract ▼ Abstract: Time-averaged images of the magnetization within single layer spin transfer oscillators have been obtained using the holography with extended reference by autocorrelation linear differential operator (HERALDO) technique. Transport measurements on a Pd(5)-Cu(20)-Ni81Fe19(7)-Cu(2)-Pd(2) (in nm) stack with a 100 nm diameter nano-contact reveal the presence of vortex dynamics. Magnetic images of the device for injected current values of 24mA and -24mA suggest that a vortex has been ejected from the nano-contact and become pinned at the edge of the region that is visible through the Au mask.	Feb 2016
I16-Materials and Magnetism	Ordering fluctuation dynamics in AuAgZn_2 Frederic Livet , Mathieu Fèvre , Guillaume Beutier , Mark Sutton Physical Review B 92 (9), 094102 DOI: 10.1103/PhysRevB.92.094102 Diamond Proposal Number(s): [630] Show Abstract ▼ Abstract: The second-order ordering transition of the AuAgZn2 alloy has been studied by coherent x-ray scattering. Within a few degrees above the critical temperature Tc, equilibrium critical fluctuations are observed together with some pretransitional local ordering connected to sample defects. The speckles observed correspond to heterodyne interference between local ordering and fluctuations and show a mixed static and dynamical behavior in a narrow domain of a few tenths of degree above Tc. The dynamical behavior is shown to correspond to the critical slowing down of the fluctuations in the vicinity of the transition (model “A” of Hohenberg and Halperin [Rev. Mod. Phys. 49, 435 (1977)]). A rough comparison can be carried out with the classical diffusion models. Some improvements of the method are discussed.	Sep 2015
I16-Materials and Magnetism	Diffuse multiple scattering Gareth Nisbet , Guillaume Beutier , Federica Fabrizi , Benjamin Moser , Steve Collins Acta Crystallographica Section A Foundations And Advances 71, 20 - 25 DOI: 10.1107/S2053273314026515 PMID: 25537385 Open Access Show Abstract ▼ Abstract: A new form of diffraction lines has been identified, similar to Rutherford, Kikuchi and Kossel lines. This paper highlights some of the properties of these lines and shows how they can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination.	Jan 2015
I16-Materials and Magnetism	An X-ray study of the Dzyaloshinskii-Moriya interaction in the weak ferromagnet FeBO3 Vladimir Dmitrienko , Elena Ovchinnikova , Steve Collins , Gareth Nisbet , Guillaume Beutier Journal Of Physics: Conference Series 519 (1) REXS 2013 — Workshop on Resonant Elastic X-ray Scattering in Condensed Matter DOI: 10.1088/1742-6596/519/1/012003 Open Access Show Abstract ▼ Abstract: We report on the axis, magnitude and direction of the Dzyaloshinskii-Moriya (DM) interaction in the weak ferromagnet FeBO3. The latter relies on the determination of the phase of the magnetic x-ray scattering amplitude. We outline a new technique based on interference with forbidden quadrupole resonant scattering to obtain this phase information.	May 2014
I16-Materials and Magnetism	Phase transition of KDP observed by Resonant X-ray Diffraction at forbidden reflections Guillaume Beutier , Steve Collins , Elena Ovchinnikova , Gareth Nisbet , Vladimir Dmitrienko Journal Of Physics: Conference Series 519 REXS 2013 — Workshop on Resonant Elastic X-ray Scattering in Condensed Matter DOI: 10.1088/1742-6596/519/1/012006 Open Access Show Abstract ▼ Abstract: We report observations of space-group-forbidden Bragg reflections in Potassium (KH2PO4), at the potassium K edge. We find clear evidence for a transition from one class of space-group-forbidden reflections, where scattering is ruled out by the electric dipole approximation, to a second class, in the ferroelectric phase, where scattering can proceed due to resonant anisotropy within the dipole approximation. The change of symmetry is clearly evidenced by the sudden change of intensity and energy spectrum of the forbidden reflections.	May 2014
I16-Materials and Magnetism	Coherent magnetic diffraction from the uranium M4 edge in the multi-k magnet, USb J. Lim , E. Blackburn , G. Beutier , F. Livet , N. Magnani , A. Bombardi , R. Caciuffo , G. H. Lander Journal Of Physics: Conference Series 519 REXS 2013 — Workshop on Resonant Elastic X-ray Scattering in Condensed Matter DOI: 10.1088/1742-6596/519/1/012010 Diamond Proposal Number(s): [8384] Open Access Show Abstract ▼ Abstract: The slow magnetic dynamics, from seconds to kiloseconds, of the canonical 3-k antiferromagnet USb have been probed, using X-ray photon correlation spectroscopy (XPCS). In this work, XPCS is combined with resonant X-ray diffraction to focus on scattering at an antiferromagnetic Bragg peak. High quality coherent magnetic diffraction patterns were recorded (speckle contrast of about 88%) and magnetic domains were observed; the number of domains increases on warming to T* about 160 K, where the spin waves soften to zero frequency, and again on warming to TN = 218 K. The intensity auto-correlation, g2(t), is primarily static over 1000 s, with a small dynamical process (change of about 0.4%) that increases in rate close to the transitions.	May 2014

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