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

Instruments / Technical Area	Publication Details	Published
I16-Materials and Magnetism	Antiferrodistortive and ferroeletric phase transitions in freestanding films of SrTiO3 Ludmila Leroy , Shih-Wen Huang , Chun-Chien Chiu , Sheng-Zhu Ho , Janine Dössegger , Cinthia Piamonteze , Yi-Chun Chen , Elsa Abreu , Alessandro Bombardi , Jan-Chi Yang , Urs Staub Nano Letters DOI: 10.1021/acs.nanolett.4c05664 Open Access Show Abstract ▼ Abstract: Thin films’ properties can be greatly influenced by their supporting growth substrates. Even in the so-called strain-free heterostructure films, it is still unclear whether there will be no interfacial electronic reconstructions induced by the underlying substrates. Here, we report the studies of SrTiO3 (STO) films in the freestanding form (FS) with a thickness ranging from 20 to 80 nm. These STO films, by default, are in a strain-free state; they exhibit distinct properties not seen in both bulk and strain-free heterostructure forms. Our films show an enhanced antiferrodistortive (AFD) phase transition temperature with a preferential in-plane rotation axis for the TiO6 octahedra. The anisotropic Ti orbital occupancy around the surface signals the departure of its properties from the bulk. Moreover, we have found that the in-plane ferroelectricity can be strengthened by the reduced dimensionality, establishing that the dimensionality control is an important factor for enhancing STO’s ferroelectric response.	May 2025
I16-Materials and Magnetism	Three-dimensional imaging of topologically protected strings in a multiferroic nanocrystal Mansoor A. Najeeb , David Serban , Daniel G. Porter , Frank Lichtenberg , Stephen P. Collins , Alessandro Bombardi , Nicola A. Spaldin , Marcus C. Newton Communications Materials 6 DOI: 10.1038/s43246-025-00738-x Diamond Proposal Number(s): [34302] Open Access Show Abstract ▼ Abstract: Multiferroic materials can host a plethora of intriguing phenomena due to the presence of multiple ferroic properties that break both spatial inversion symmetry and time reversal symmetry at an observable scale. Hexagonal manganite multiferroics are of particular interest as the properties of their symmetry-lowering phase transition can be described by a Mexican-hat-like potential energy surface. The early universe is proposed to have undergone a symmetry-lowering phase transition that is described by a similar Mexican-hat-like potential that gives rise to the formation of one-dimensional topologically protected defects known as cosmic strings. According to the Kibble-Zurek mechanism, hexagonal manganite multiferroics can host the crystallographic equivalent of cosmic strings and can therefore serve as a testing ground for exploration of concepts in cosmology. To date, however, direct imaging of 1D topological defects in a condensed matter material system has not been achieved. Here we report on robust three-dimensional imaging of topologically protected strings in a single hexagonal manganite nanocrystal, enabled by advances in experimental techniques. Our findings reveal multiferroic strings with a preferred phase vortex winding direction and average separation of ~93 nm.	Jan 2025
I16-Materials and Magnetism	Imaging of electric-field-induced domain structure in DyMnO3 nanocrystals Mansoor A. Najeeb , Robbie Morrison , Ahmed H. Mokhtar , Daniel G. Porter , Frank Lichtenberg , Alessandro Bombardi , Marcus C. Newton Discover Nano 19 DOI: 10.1186/s11671-024-04165-8 Diamond Proposal Number(s): [33320] Open Access Show Abstract ▼ Abstract: Multiferroic materials that exhibit interacting and coexisting properties, like ferroelectricity and ferromagnetism, possess significant potential in the development of novel technologies that can be controlled through the application of external fields. They also exhibit varying regions of polarity, known as domains, with the interfaces that separate the domains referred to as domain walls. In this study, using three-dimensional (3D) bragg coherent diffractive imaging (BCDI), we investigate the dynamics of multiferroic domain walls in a single hexagonal dysprosium manganite (h-DyMnO ) nanocrystal under varying applied electric field. Our analysis reveals that domain wall motion is influenced by the pinning effects, and a threshold voltage of +3 V is required to overcome them. Using circular mean analysis and phase gradient mapping, we identified localised phase realignment and high-gradient regions corresponding to domain walls, providing insights into the behaviour of multiferroic systems under external stimuli.	Dec 2024
I16-Materials and Magnetism	Three-dimensional imaging of the structural phase transition in a single vanadium dioxide nanocrystal Mansoor A. Najeeb , Ahmed H. Mokhtar , David A. Serban , Daniel G. Porter , Stephen Collins , Alessandro Bombardi , Marcus C. Newton Physica Status Solidi (a) 19 DOI: 10.1002/pssa.202400503 Diamond Proposal Number(s): [22270] Open Access Show Abstract ▼ Abstract: Vanadium dioxide (VO2) is a strongly correlated material that exhibits a number of structural phase transitions (SPT) near to room temperature of considerable utility for various technological applications. When reduced to the nanoscale, a foreknowledge of surface and interface properties of VO2 during the SPT can facilitate the development of devices based on VO2. Herein, it is shown that Bragg coherent X-ray diffractive imaging (BCDI) combined with machine learning is an effective means to recover three-dimensional images of a single VO2 nanocrystal during a temperature-induced SPT from a room-temperature monoclinic phase to a high-temperature rutile phase. The findings reveal the coexistence of multiple phases within the nanocrystal throughout the transition, along with missing density which indicates the presence of a newly formed rutile phase.	Nov 2024
I13-1-Coherence I16-Materials and Magnetism	Imaging in-operando LiCoO2 nanocrystallites with Bragg coherent X-ray diffraction David Serban , Daniel G. Porter , Ahmed H. Mokhtar , Mansoor Nellikkal , Sivaperuma Uthayakumar , Min Zhang , Stephen P. Collins , Alessandro Bombardi , Peng Li , Christoph Rau , Marcus Newton Communications Chemistry 7 DOI: 10.1038/s42004-024-01331-y Diamond Proposal Number(s): [31929, 34075, 34025, 29880, 27621] Open Access Show Abstract ▼ Abstract: Although the LiCoO2 (LCO) cathode material has been widely used in commercial lithium ion batteries (LIB) and shows high stability, LIB’s improvements have several challenges that still need to be overcome. In this paper, we have studied the in-operando structural properties of LCO within battery cells using Bragg Coherent X-ray Diffraction Imaging to identify ways to optimise the LCO batteries’ cycling. We have successfully reconstructed the X-ray scattering phase variation (a fingerprint of atomic displacement) within a ≈ (1.6 × 1.4 × 1.3) μm3 LCO nanocrystal across a charge/discharge cycle. Reconstructions indicate strained domains forming, expanding, and fragmenting near the surface of the nanocrystal during charging, with a determined maximum relative lattice displacements of 0.467 Å. While discharging, all domains replicate in reverse the effects observed from the charging states, but with a lower maximum relative lattice displacements of 0.226 Å. These findings show the inefficiency-increasing domain dynamics within LCO lattices during cycling.	Oct 2024
I16-Materials and Magnetism	Spontaneous reversal of spin chirality and competing phases in the topological magnet EuAl4 Anuradha M. Vibhakar , Dmitry D. Khalyavin , Fabio Orlandi , Jaime M. Moya , Shiming Lei , Emilia Morosan , Alessandro Bombardi Communications Physics 7 DOI: 10.1038/s42005-024-01802-7 Diamond Proposal Number(s): [31813, 35465] Open Access Show Abstract ▼ Abstract: Materials exhibiting a spontaneous reversal of spin chirality have the potential to drive the widespread adoption of chiral magnets in spintronic devices. Unlike the majority of chiral magnets that require the application of an external field to reverse the spin chirality, we observe the spin chirality to spontaneously reverse in the topological magnet EuAl4. Using resonant elastic x-ray scattering we demonstrate that all four magnetic phases in EuAl4 are single-k, where the first two magnetic phases are characterized by spin density wave order and the last two by helical spin order. A single spin chirality was stabilised across the 1mm2 sample, and the reversal of spin chirality occurred whilst maintaining a helical magnetic structure. At the onset of the helical magnetism, the crystal symmetry lowers to a chiral monoclinic space group, explaining the asymmetry in the chiral spin order, and establishing a mechanism by which the spin chirality could reverse via magnetostructural coupling.	Sep 2024
I16-Materials and Magnetism	Strain-induced antiferromagnetic domain switching via the spin Jahn-Teller effect Dylan Behr , Leonid S. Taran , Daniel G. Porter , Alessandro Bombardi , Dharmalingam Prabhakaran , Sergey V. Streltsov , Roger D. Johnson Physical Review B 110 DOI: 10.1103/PhysRevB.110.L060408 Diamond Proposal Number(s): [32034] Open Access Show Abstract ▼ Abstract: The spin Jahn-Teller effect, where a degeneracy of magnetic ground states is spontaneously lifted by structural distortions, lends itself to exploitation by the implied magnetoelastic coupling. CoTi2⁢O5 hosts a frustrated topology of magnetic interactions that could realize such coupling, since the observed magnetic ground state requires a spontaneous monoclinic distortion of the crystal. Using resonant elastic x-ray scattering to simultaneously probe the magnetic structure and lattice distortion of CoTi2⁢O5, we demonstrate near complete magnetic domain switching by an applied uniaxial stress that is conjugate to the monoclinic strain. Our results, supported by density functional theory calculations, confirm that CoTi2⁢O5 displays spin Jahn-Teller effects that can be understood in terms of modulated Heisenberg exchange interactions, and demonstrate the potential functionality of spin Jahn-Teller materials in spintronic devices sensitive to uniaxial strain.	Aug 2024
I16-Materials and Magnetism	Imaging and ferroelectric orientation mapping of photostriction in a single Bismuth Ferrite nanocrystal Ahmed H. Mokhtar , David Serban , Daniel G. Porter , Gareth Nisbet , Steve Collins , Alessandro Bombardi , Marcus C. Newton Npj Computational Materials 10 DOI: 10.1038/s41524-024-01287-6 Diamond Proposal Number(s): [25437] Open Access Show Abstract ▼ Abstract: The exploration of multiferroic materials and their interaction with light at the nanoscale presents a captivating frontier in materials science. Bismuth Ferrite (BiFeO3, BFO), a standout among these materials, exhibits room-temperature ferroelectric and antiferromagnetic behaviour and magnetoelectric coupling. Of particular interest is the phenomenon of photostriction, the light-induced deformation of crystal structures, which enhances the prospect for device functionality based on these materials. Understanding and harnessing multiferroic phenomena holds significant promise in various technological applications, from optoelectronics to energy storage. The orientation of the ferroelectric axis is an important design parameter for devices formed from multiferroic materials. Determining its orientation in the laboratory frame of reference usually requires knowing multiple wavevector transfer (Q-Vector) directions, which can be challenging to establish due to the need for extensive reciprocal-space searches. Our study demonstrates a method to identify the ferroelectric axis orientation using Bragg Coherent X-ray Diffraction Imaging (BCDI) measurements at a single Q-vector direction. This method involves applying photostriction-inducing laser illumination across various laser polarisations. Our findings reveal that photostriction primarily occurs as a surface phenomenon at the nanoscale. Moreover, a photo-induced crystal length change ranging from 30 to 60 nm was observed, consistent with earlier findings on bulk material.	May 2024
I16-Materials and Magnetism	Magnetism in the axion insulator candidate Eu5In2Sb6 M. C. Rahn , M. N. Wilson , T. J. Hicken , F. L. Pratt , C. Wang , F. Orlandi , D. D. Khalyavin , P. Manuel , L. S. I. Veiga , A. Bombardi , S. Francoual , P. Bereciartua , A. S. Sukhanov , J. D. Thompson , S. M. Thomas , P. F. S. Rosa , T. Lancaster , F. Ronning , M. Janoschek Physical Review B 109 DOI: 10.1103/PhysRevB.109.174404 Open Access Show Abstract ▼ Abstract: Eu 5 In 2 Sb 6 is a member of a family of orthorhombic nonsymmorphic rare-earth intermetallics that combines large localized magnetic moments and itinerant exchange with a low carrier density and perpendicular glide planes. This may result in special topological crystalline (wallpaper fermion) or axion insulating phases. Recent studies of Eu 5 In 2 Sb 6 single crystals have revealed colossal negative magnetoresistance and multiple magnetic phase transitions. Here, we clarify this ordering process using neutron scattering, resonant elastic x-ray scattering, muon spin-rotation, and magnetometry. The nonsymmorphic and multisite character of Eu 5 In 2 Sb 6 results in coplanar noncollinear magnetic structures with an Ising-like net magnetization along the a axis. A reordering transition, attributable to competing ferro- and antiferromagnetic couplings, manifests as the onset of a second commensurate Fourier component. In the absence of spatially resolved probes, the experimental evidence for this low-temperature state can be interpreted either as an unusual double- q structure or in a phase separation scenario. The net magnetization produces variable anisotropic hysteretic effects which also couple to charge transport. The implied potential for functional domain physics and topological transport suggests that this structural family may be a promising platform to implement concepts of topological antiferromagnetic spintronics.	May 2024
I16-Materials and Magnetism	Three-dimensional domain identification in a single hexagonal manganite nanocrystal Ahmed H. Mokhtar , David Serban , Daniel G. Porter , Frank Lichtenberg , Stephen P. Collins , Alessandro Bombardi , Nicola A. Spaldin , Marcus C. Newton Nature Communications 15 DOI: 10.1038/s41467-024-48002-z Diamond Proposal Number(s): [30073] Open Access Show Abstract ▼ Abstract: The three-dimensional domain structure of ferroelectric materials significantly influences their properties. The ferroelectric domain structure of improper multiferroics, such as YMnO3, is driven by a non-ferroelectric order parameter, leading to unique hexagonal vortex patterns and topologically protected domain walls. Characterizing the three-dimensional structure of these domains and domain walls has been elusive, however, due to a lack of suitable imaging techniques. Here, we present a multi-peak Bragg coherent x-ray diffraction imaging determination of the domain structure in single YMnO3 nanocrystals. We resolve two ferroelectric domains separated by a domain wall and confirm that the primary atomic displacements occur along the crystallographic c-axis. Correlation with atomistic simulations confirms the Mexican hat symmetry model of domain formation, identifying two domains with opposite ferroelectric polarization and adjacent trimerization, manifesting in a clockwise arrangement around the hat’s brim.	Apr 2024

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