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99 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
I15-Extreme Conditions	Acceptor doping and actuation mechanisms in Sr-doped BiFeO3BaTiO3 ceramics Ziqi Yang , Yizhe Li , Bing Wang , Juncheng Pan , Annette K. Kleppe , David Hall Journal Of Materiomics 71 DOI: 10.1016/j.jmat.2023.04.007 Diamond Proposal Number(s): [30553] Open Access Show Abstract ▼ Abstract: BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0 at%, on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3 at %) yielded enhanced ferroelectric (Pmax ~ 0.37 C m-2, Pr ~ 0.30 C m-2) and piezoelectric (d33 ~ 178 pC N-1, kp ~ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.	May 2023
I11-High Resolution Powder Diffraction	Insights into the structural symmetry of YCrO3 from synchrotron X-ray diffraction Qian Zhao , Kaitong Sun , Yinghao Zhu , Zirui Zhao , Hai-Feng Li Journal Of Applied Crystallography 55 DOI: 10.1107/S1600576722009438 Show Abstract ▼ Abstract: A high-resolution synchrotron X-ray diffraction study of a single-crystal YCrO3 compound was employed to obtain its crystallographic information, such as lattice parameters, atomic positions, bond lengths and angles, and local crystalline distortion size and mode. The measurements were taken at 120 K (below the antiferromagnetic transition temperature TN ≃ 141.5 K), 300 K (between TN and the ferroelectric transition temperature TC ≃ 473 K) and 500 K (above TC). Using the high intensity of synchrotron X-rays, it was possible to refine collected patterns with the previously proposed noncentrosymmetric monoclinic structural model (P1211, No. 4) and determine detailed structural parameters. Meanwhile, for a controlled study, the data were refined with the centrosymmetric orthorhombic space group (Pmnb, No. 62). The lattice constants a, b and c and the unit-cell volume increased nearly linearly upon heating. With the P1211 space group, the distributions of bond lengths and angles, as well as local distortion strengths, were observed to be more dispersed. This implies that (i) the local distortion mode of Cr2O6 at 120 K correlates with the formation of canted antiferromagnetic order by Cr1–Cr2 spin interactions, primarily via intermediate O3 and O4 ions; and (ii) the previously reported dielectric anomaly may have a microscopic origin in the strain-balanced Cr1—O3(O4) and Cr2—O5(O6) bonds as well as the local distortion modes of Cr1O6 and Cr2O6 octahedra at 300 K. Local crystalline distortion is shown to be an important factor in the formation of ferroelectric order. The comprehensive set of crystallographic information reported here allows for a complete understanding of the unique magnetic and ferroelectric properties of YCrO3.	Dec 2022
B18-Core EXAFS	Bi2CoO2F4-a polar, ferrimagnetic aurivillius oxide-fluoride Euan A. S. Scott , Eleni Mitoudi Vagourdi , Mats Johnsson , Vanessa Cascos , Filbin John , Dave Pickup , Alan V. Chadwick , Hania Djani , Eric Bousquet , Weiguo Zhang , P. Shiv Halasyamani , Emma E. Mccabe Chemistry Of Materials 39 DOI: 10.1021/acs.chemmater.2c02745 Open Access Show Abstract ▼ Abstract: Aurivillius oxides have been a research focus due to their ferroelectric properties, but by replacing oxide ions by fluoride, divalent magnetic cations can be introduced, giving Bi2MO2F4 (M = Fe, Co, and Ni). Our combined experimental and computational study on Bi2CoO2F4 indicates a low-temperature polar structure of P21ab symmetry (analogous to ferroelectric Bi2WO6) and a ferrimagnetic ground state. These results highlight the potential of Aurivillius oxide-fluorides for multiferroic properties. Our research has also revealed some challenges associated with the reduced tendency for polar displacements in the more ionic fluoride-based systems.	Oct 2022
I11-High Resolution Powder Diffraction	Synthesis and characterization of magnetoelectric Ba7Mn4O15 Gabriel R. M. Clarke , Martin R. Lees , Clemens Ritter , Ivan Da Silva , Mark S. Senn Inorganic Chemistry DOI: 10.1021/acs.inorgchem.2c00889 Diamond Proposal Number(s): [25166] Open Access Show Abstract ▼ Abstract: We present the synthesis of a novel binary metal oxide material: Ba7Mn4O15. The crystal structure has been investigated by high-resolution powder synchrotron X-ray diffraction in the temperature range of 100–300 K as well as by powder neutron diffraction at 10 and 80 K. This material represents an isostructural barium-substituted analogue of the layered material Sr7Mn4O15 that forms its own structural class. However, we find that Ba7Mn4O15 adopts a distinct magnetic ordering, resulting in a magnetoelectric ground state below 50 K. The likely magnetoelectric coupling mechanisms have been inferred from performing a careful symmetry-adapted refinement against the powder neutron diffraction experiments, as well as by making a comparison with the nonmagnetoelectric ground state of Sr7Mn4O15.	Jun 2022
I11-High Resolution Powder Diffraction I15-Extreme Conditions	Quenching effects and mechanisms in bismuth-based perovskite ferroelectrics Lalitha Kodumudi Venkataraman , Bing Wang , Pengrong Ren , David A. Hall , Tadej Rojac Open Ceramics 17 DOI: 10.1016/j.oceram.2022.100259 Diamond Proposal Number(s): [14061, 17673, 16390] Open Access Show Abstract ▼ Abstract: The similar electronic structures of Bi3+ and Pb2+ have motivated researchers to explore bismuth-based perovskite compounds, which in the past decade has been further fuelled by the demand for developing lead-free piezoceramics. The difficulty in stabilizing the perovskite phase in bismuth based compounds has directed most research activities towards exploring two main compounds - multiferroic BiFeO3 and relaxor ferroelectric Na1/2Bi1/2TiO3 and their derivatives. In recent years, quenching these materials from the sintering temperature or from the paraelectric phase (above the Curie temperature, Tc) has resulted in a plethora of fundamentally interesting and technologically relevant advances, including enhanced thermal depolarization temperature, high Tc, giant strain and control over the atomic structure and electrical conductivity at the domain wall. In this contribution, a brief overview of quenching piezoceramics is presented, with majority of the discussion encompassing salient features of quenching lead-free perovskite structured Na1/2Bi1/2TiO3- and BiFeO3- based materials. For each material system, the influence of quenching on phase transitions, domain switching behavior and electromechanical properties are presented, apart from outlining the current understanding of the underlying mechanisms. The review provides guidelines for further exploration of the quenching strategy for improving the functionality of Bi-based piezoceramics.	May 2022
I06-Nanoscience	XPEEM and MFM imaging of ferroic materials Massimo Ghidini , Francesco Maccherozzi , Sarnjeet S. Dhesi , Neil D. Mathur Advanced Electronic Materials 13 DOI: 10.1002/aelm.202200162 Diamond Proposal Number(s): [19060] Open Access Show Abstract ▼ Abstract: The authors describe and compare two complementary techniques that are habitually used to image ferromagnetic and ferroelectric materials with sub-micron spatial resolutions (typically 50 nm, at best 10 nm). The first technique is variable-temperature photoemission electron microscopy with magnetic/antiferromagnetic/polar contrast from circularly/linearly polarized incident X-rays (XPEEM). The second technique is magnetic force microscopy (MFM). Focusing mainly on the authors’ own work, but not exclusively, published/unpublished XPEEM and MFM images of ferroic domains and complex magnetic textures (involving vortices and phase separation) are presented. Highlights include the use of two XPEEM images to create 2D vector maps of in-plane (IP) magnetization, and the use of imaging to detect electrically driven local reversals of magnetization. The brief and simple descriptions of XPEEM and MFM should be useful for beginners seeking to employ these techniques in order to understand and harness ferroic materials.	May 2022
I11-High Resolution Powder Diffraction I15-Extreme Conditions	Microscopic mechanisms in multiferroic materials Gabriel Richard Michael Clarke Show Abstract ▼ Abstract: Ferroic materials are of fundamental importance in the modern world with applications ranging from sensors to computational memory and beyond, and multiferroic materials displaying several ferroic properties simultaneously have a great deal of potential for future devices. The antiferromagnetic Sr7Mn4O15 phase was recently identified as a potential multiferroic material. Chapters 2 and 3 explore the synthetic conditions necessary to expand the solid solution Sr7-xAxMn4O15 for A: Ca2+ and Ba2+. The structure is investigated using X-ray and neutron diffraction methods under variation of chemical substitution, temperature and hydrostatic pressure. Magnetic analysis is also performed using direct current magnetic susceptibility measurements, and long-range spin orderings are identified using low-temperature neutron diffraction experiments. Several novel compositions are synthesised and characterised; in particular, the Ba7Mn4O15 composition described in Chapter 3 exhibits a magnetoelectric ground state below 50 K. The second half of this thesis is concerned with the responses of hybrid improper ferroelectric n = 2 Ruddlesden-Popper phases to hydrostatic pressure and electric fields. Chapter 4 describes a high-pressure experiment on Ca3Mn2O7 and Ca3Ti2O7, with accompanying computational analysis showing that both phases undergo a ferroelectric phase transition to a non-polar phase above 1 GPa and 30 GPa, respectively. Despite this, the relative energies of the polar and non-polar phases unexpectedly show that the polar phase is actually stabilised by increased pressure, meaning that the polarisation itself may increase with pressure up to a limit, contrary to the trend normally observed in proper ferroelectrics. Chapter 5 reports an in situ synchrotron X-ray diffraction experiment on the substituted phase Ca2.15Sr0.85Ti2O7 in which compressed powder samples were subjected to an applied electric field while diffraction patterns were measured. The output time-resolved data are analysed to attempt to identify how ferroelectric switching may proceed in this and related phases, with octahedral rotations being identified as a plausible pathway. Throughout all chapters, the symmetries and phase transitions of the various materials are analysed through representation analysis.	Mar 2022
I16-Materials and Magnetism	Ferroelectric incommensurate spin crystals Dorin Rusu , Jonathan J. P. Peters , Thomas P. A. Hase , James A. Gott , Gareth A. A. Nisbet , Jörg Strempfer , Daniel Haskel , Samuel D. Seddon , Richard Beanland , Ana M. Sanchez , Marin Alexe Nature 602, 240 - 244 DOI: 10.1038/s41586-021-04260-1 Diamond Proposal Number(s): [25569] Open Access Show Abstract ▼ Abstract: Ferroics, especially ferromagnets, can form complex topological spin structures such as vortices1 and skyrmions when subjected to particular electrical and mechanical boundary conditions. Simple vortex-like, electric-dipole-based topological structures have been observed in dedicated ferroelectric systems, especially ferroelectric–insulator superlattices such as PbTiO3/SrTiO3, which was later shown to be a model system owing to its high depolarizing field. To date, the electric dipole equivalent of ordered magnetic spin lattices driven by the Dzyaloshinskii–Moriya interaction (DMi) has not been experimentally observed. Here we examine a domain structure in a single PbTiO3 epitaxial layer sandwiched between SrRuO3 electrodes. We observe periodic clockwise and anticlockwise ferroelectric vortices that are modulated by a second ordering along their toroidal core. The resulting topology, supported by calculations, is a labyrinth-like pattern with two orthogonal periodic modulations that form an incommensurate polar crystal that provides a ferroelectric analogue to the recently discovered incommensurate spin crystals in ferromagnetic materials. These findings further blur the border between emergent ferromagnetic and ferroelectric topologies, clearing the way for experimental realization of further electric counterparts of magnetic DMi-driven phases.	Feb 2022
I21-Resonant Inelastic X-ray Scattering (RIXS)	Multiferroic enabled magnetic-exciton in 2D quantum entangled van der Waals antiferromagnet NiI2 Suhan Son , Youjin Lee , Jae Ha Kim , Beom Hyun Kim , Chaebin Kim , Woongki Na , Hwiin Ju , Sudong Park , Abhishek Nag , Ke-Jin Zhou , Young-Woo Son , Hyeongdo Kim , Woo-Suk Noh , Jae-Hoon Park , Jong Seok Lee , Hyeonsik Cheong , Jae Hoon Kim , Je-Geun Park Advanced Materials DOI: 10.1002/adma.202109144 Diamond Proposal Number(s): [29554] Show Abstract ▼ Abstract: Matter-light interaction is at the center of diverse research fields from quantum optics to condensed matter physics, opening new fields like laser physics. A magnetic exciton is one such rare example found in magnetic insulators. However, it is relatively rare to observe that external variables control matter-light interaction. Here, we report that the broken inversion symmetry of multiferroicity can act as an external knob enabling the magnetic exciton in van der Waals antiferromagnet NiI2. We further discover that this magnetic exciton arises from a transition between Zhang-Rice-triplet and Zhang-Rice-singlet's fundamentally quantum entangled states. This quantum entanglement produces an ultra-sharp optical exciton peak at 1.384 eV with a 5 meV linewidth. Our work demonstrates that NiI2 is two-dimensional magnetically ordered with an intrinsically quantum entangled ground state.	Dec 2021
I11-High Resolution Powder Diffraction	Directed synthesis of a hybrid improper magnetoelectric multiferroic material Tong Zhu , Fabio Orlandi , Pascal Manuel , Alexandra S. Gibbs , Weiguo Zhang , P. Shiv Halasyamani , Michael A. Hayward Nature Communications 12 DOI: 10.1038/s41467-021-25098-1 Diamond Proposal Number(s): [13284] Open Access Show Abstract ▼ Abstract: Preparing materials which simultaneously exhibit spontaneous magnetic and electrical polarisations is challenging as the electronic features which are typically used to stabilise each of these two polarisations in materials are contradictory. Here we show that by performing low-temperature cation-exchange reactions on a hybrid improper ferroelectric material, Li2SrTa2O7, which adopts a polar structure due to a cooperative tilting of its constituent TaO6 octahedra rather than an electronically driven atom displacement, a paramagnetic polar phase, MnSrTa2O7, can be prepared. On cooling below 43 K the Mn2+ centres in MnSrTa2O7 adopt a canted antiferromagnetic state, with a small spontaneous magnetic moment. On further cooling to 38 K there is a further transition in which the size of the ferromagnetic moment increases coincident with a decrease in magnitude of the polar distortion, consistent with a coupling between the two polarisations.	Aug 2021

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