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

Instruments / Technical Area	Publication Details	Published
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
I10-Beamline for Advanced Dichroism	Demonstration of a thickness-step Skyrmion Injector in FeGe Murray Wilson , Geetha Balakrishnan , Peter D. Hatton , Luke A. Turnbull , Samuel H. Moody , Matthew T. Littlehales , Raymond Fan , Paul Steadman APS March Meeting 2023 Diamond Proposal Number(s): [30616, 31619] Show Abstract ▼ Abstract: https://meetings.aps.org/Meeting/MAR23/Session/W54.7	Mar 2023
I10-Beamline for Advanced Dichroism	X-ray holographic imaging of magnetic surface spirals in FeGe lamellae L. A. Turnbull , M. T. Littlehales , M. N. Wilson , M. T. Birch , H. Popescu , N. Jaouen , J. A. T. Verezhak , G. Balakrishnan , P. D. Hatton Physical Review B 106 DOI: 10.1103/PhysRevB.106.064422 Diamond Proposal Number(s): [27196] Show Abstract ▼ Abstract: Isotropic helimagnets are known to host a diverse range of chiral magnetic states. In 2016, Rybakov et al., theorized the presence of a surface-pinned stacked spin spiral phase [F. N. Rybakov et al., New J. Phys. 18, 045002 (2016)], which has yet to be observed experimentally. The phase is characterized by surface spiral periods exceeding the host material's fundamental winding period L D . Here, we present experimental evidence for the observation of this state in lamellae of FeGe using resonant x-ray holographic imaging data and micromagnetic simulations. We find images of FeGe lamellae, exceeding a critical thickness of 300 nm ( 4.3 L D ), exhibit contrast modulations with a field-dependent periodicity of λ ≥ 1.4 L D , consistent with theoretical predictions of the stacked spiral state. The identification of this spiral state has significant implications for the stability of other coexisting spin textures, and will help complete our understanding of helimagnetic systems.	Aug 2022
NONE-No attached Diamond beamline	Topological defect-mediated skyrmion annihilation in three dimensions Max T. Birch , David Cortés-Ortuño , Nguyen D. Khanh , Shinichiro Seki , Ales Stefancic , Geetha Balakrishnan , Yoshinori Tokura , Peter D. Hatton Communications Physics 4 DOI: 10.1038/s42005-021-00675-4 Open Access Show Abstract ▼ Abstract: The creation and annihilation of magnetic skyrmions are mediated by three-dimensional topological defects known as Bloch points. Investigation of such dynamical processes is important both for understanding the emergence of exotic topological spin textures, and for future engineering of skyrmions in technological applications. However, while the annihilation of skyrmions has been extensively investigated in two dimensions, in three dimensions the phase transitions are considerably more complex. We report field-dependent experimental measurements of metastable skyrmion lifetimes in an archetypal chiral magnet, revealing two distinct regimes. Comparison to supporting three-dimensional geodesic nudged elastic band simulations indicates that these correspond to skyrmion annihilation into either the helical and conical states, each exhibiting a different transition mechanism. The results highlight that the lowest energy magnetic configuration of the system plays a crucial role when considering the emergence and stability of topological spin structures via defect-mediated dynamics.	Aug 2021
I10-Beamline for Advanced Dichroism	Deriving the skyrmion Hall angle from skyrmion lattice dynamics Richard Brearton , L. A. Turnbull , J. A. T. Verezhak , G. Balakrishnan , P. D. Hatton , G. Van Der Laan , T. Hesjedal Nature Communications 12 DOI: 10.1038/s41467-021-22857-y Diamond Proposal Number(s): [23784, 23451] Open Access Show Abstract ▼ Abstract: Magnetic skyrmions are topologically non-trivial, swirling magnetization textures that form lattices in helimagnetic materials. These magnetic nanoparticles show promise as high efficiency next-generation information carriers, with dynamics that are governed by their topology. Among the many unusual properties of skyrmions is the tendency of their direction of motion to deviate from that of a driving force; the angle by which they diverge is a materials constant, known as the skyrmion Hall angle. In magnetic multilayer systems, where skyrmions often appear individually, not arranging themselves in a lattice, this deflection angle can be easily measured by tracing the real space motion of individual skyrmions. Here we describe a reciprocal space technique which can be used to determine the skyrmion Hall angle in the skyrmion lattice state, leveraging the properties of the skyrmion lattice under a shear drive. We demonstrate this procedure to yield a quantitative measurement of the skyrmion Hall angle in the room-temperature skyrmion system FeGe, shearing the skyrmion lattice with the magnetic field gradient generated by a single turn Oersted wire.	May 2021
I10-Beamline for Advanced Dichroism	Tilted X-ray holography of magnetic bubbles in MnNiGa lamellae Luke A. Turnbull , Max T. Birch , Angus Laurenson , Nick Bukin , Erick O. Burgos-Parra , Horia Popescu , Murray N. Wilson , Ales Stefancic , Geetha Balakrishnan , Feodor Y. Ogrin , Peter D. Hatton Acs Nano DOI: 10.1021/acsnano.0c07392 Diamond Proposal Number(s): [20866] Open Access Show Abstract ▼ Abstract: Nanoscopic lamellae of centrosymmetric ferromagnetic alloys have recently been reported to host the biskyrmion spin texture; however, this has been disputed as the misidentication of topologically trivial type-II magnetic bubbles. Here we demonstrate resonant soft X-ray holographic imaging of topological magnetic states in lamellae of the centrosymmetric alloy (Mn1–xNix)0.65Ga0.35 (x = 0.5), showing the presence of magnetic stripes evolving into single core magnetic bubbles. We observe rotation of the stripe phase via the nucleation and destruction of disclination defects. This indicates the system behaves as a conventional uniaxial ferromagnet. By utilizing the holography with extended reference by autocorrelation linear dierential operator (HERALDO) method, we show tilted holographic images at 30° incidence confirming the presence of type-II magnetic bubbles in this system. This study demonstrates the utility of X-ray imaging techniques in identifying the topology of localized structures in nanoscale magnetism.	Oct 2020
I05-ARPES I10-Beamline for Advanced Dichroism	Direct observation of the energy gain underpinning ferromagnetic superexchange in the electronic structure of CrGeTe3 Matthew D. Watson , Igor Markovic , Federico Mazzola , Akhil Rajan , Edgar A. Morales , David Burn , Thorsten Hesjedal , Gerrit Van Der Laan , Saumya Mukherjee , Timur K. Kim , Chiara Bigi , Ivana Vobornik , Monica Ciomaga Hatnean , Geetha Balakrishnan , Philip D. C. King Physical Review B 101 DOI: 10.1103/PhysRevB.101.205125 Diamond Proposal Number(s): [21986, 22794, 23785] Show Abstract ▼ Abstract: We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, CrGeTe3. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through TC. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te 5p and the Cr eg orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr t2g states that carry the majority of the spin moment. The t2g states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.	May 2020
I10-Beamline for Advanced Dichroism	Real-space imaging of confined magnetic skyrmion tubes M. T. Birch , D. Cortés-Ortuño , L. A. Turnbull , M. N. Wilson , F. Groß , N. Träger , A. Laurenson , N. Bukin , S. H. Moody , M. Weigand , G. Schütz , H. Popescu , R. Fan , P. Steadman , J. A. T. Verezhak , G. Balakrishnan , J. C. Loudon , A. C. Twitchett-Harrison , O. Hovorka , H. Fangohr , F. Y. Ogrin , J. Gräfe , P. D. Hatton Nature Communications 11 DOI: 10.1038/s41467-020-15474-8 Diamond Proposal Number(s): [20866] Open Access Show Abstract ▼ Abstract: Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they are commonly portrayed as two dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the host material. The study of this skyrmion tube state (SkT) is vital for furthering the understanding of skyrmion formation and dynamics for future applications. However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure. The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigation into this unexplored dimension of the skyrmion spin texture.	Apr 2020
I09-Surface and Interface Structural Analysis	Proximity-induced ferromagnetism and chemical reactivity in few-layer VSe 2 heterostructures G. Vinai , C. Bigi , A. Rajan , M. D. Watson , T.-L. Lee , F. Mazzola , S. Modesti , S. Barua , M. Ciomaga Hatnean , G. Balakrishnan , P. D. C. King , P. Torelli , G. Rossi , G. Panaccione Physical Review B 101 DOI: 10.1103/PhysRevB.101.035404 Diamond Proposal Number(s): [21429] Show Abstract ▼ Abstract: Among transition-metal dichalcogenides, mono and few-layers thick VSe 2 has gained much recent attention following claims of intrinsic room-temperature ferromagnetism in this system, which have nonetheless proved controversial. Here, we address the magnetic and chemical properties of Fe / VSe 2 heterostructure by combining element sensitive x-ray absorption spectroscopy and photoemission spectroscopy. Our x-ray magnetic circular dichroism results confirm recent findings that both native mono/few-layer and bulk VSe 2 do not show intrinsic ferromagnetic ordering. Nonetheless, we find that ferromagnetism can be induced, even at room temperature, after coupling with a Fe thin film layer, with antiparallel alignment of the moment on the V with respect to Fe. We further consider the chemical reactivity at the Fe / VSe 2 interface and its relation with interfacial magnetic coupling.	Jan 2020
I10-Beamline for Advanced Dichroism	Stability and metastability of skyrmions in thin lamellae of Cu2OSeO3 M. N. Wilson , M. T. Birch , A. Stefancic , A. C. Twitchett-Harrison , G. Balakrishnan , T. J. Hicken , R. Fan , P. Steadman , P. D. Hatton Physical Review Research 2 DOI: 10.1103/PhysRevResearch.2.013096 Diamond Proposal Number(s): [19421] Open Access Show Abstract ▼ Abstract: We report small-angle x-ray scattering measurements of the skyrmion lattice in two 200-nm-thick Cu 2 OSeO 3 lamellae aligned with the applied magnetic field parallel to the out of plane [110] or [100] crystallographic directions. Our measurements show that the equilibrium skyrmion phase in both samples is expanded significantly compared to bulk crystals, existing between approximately 30 and 50 K over a wide region of magnetic field. This skyrmion state is elliptically distorted at low fields for the [110] sample, and symmetric for the [100] sample, possibly due to crystalline anisotropy becoming more important at this sample thickness than it is in bulk samples. Furthermore, we find that a metastable skyrmion state can be observed at low temperature by field cooling through the equilibrium skyrmion pocket in both samples. In contrast to the behavior in bulk samples, the volume fraction of metastable skyrmions does not significantly depend on cooling rate. We show that a possible explanation for this is the change in the lowest temperature of the skyrmion state in this lamellae compared to bulk, without requiring different energetics of the skyrmion state.	Jan 2020

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