I19-Small Molecule Single Crystal Diffraction
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Jakob
Nagl
,
Kirill Yu.
Povarov
,
Benjamin
Duncan
,
Catharina
Näppi
,
Dmitry
Khalyavin
,
Pascal
Manuel
,
Fabio
Orlandi
,
Jeremy
Sourd
,
Beat Valentin
Schwarze
,
Freya
Husstedt
,
Sergei A.
Zvyagin
,
Oksana
Zaharko
,
Paul
Steffens
,
Arno
Hiess
,
David R.
Allan
,
Sarah A.
Barnett
,
Zewu
Yan
,
Severian
Gvasaliya
,
Andrey
Zheludev
Diamond Proposal Number(s):
[39239]
Open Access
Abstract: The prospect of merging the paradigms of geometric frustration on a triangular lattice and bond anisotropies in the strong spin-orbit coupling limit holds tremendous promise in the search for exotic quantum materials. Here we identify a new candidate system to realize such physics, the organic quantum antiferromagnet (CD3ND3)2NaRuCl6. We report a combination of thermodynamic, magneto-elastic and neutron scattering experiments on single-crystals to determine the phase diagram in axial magnetic fields H∥c and propose a minimal model Hamiltonian. (CD3ND3)2NaRuCl6 displays an ideal triangular arrangement of Ru3+ ions adopting the spin-orbital entangled jeff = 1/2 state. It hosts residual magnetic order below TN = 0.23 K and a highly unusual H − T phase diagram including three different incommensurate states. Spin-waves in the high-field polarized regime are described by a Heisenberg triangular lattice Hamiltonian with a potential sub-leading bond dependent anisotropy term J±±. We argue that the multi-q ground state in zero magnetic field is a prime candidate for hosting the
vortex crystal proposed on the triangular Heisenberg-Kitaev model. (CD3ND3)2NaRuCl6 is the first member in an extended family of quantum triangular lattice magnets, providing a new playground to study the interplay of geometric frustration and spin-orbit effects.
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May 2026
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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James M. A.
Steele
,
Joshua D.
Bocarsly
,
Liam A. V.
Nagle-Cocco
,
George S.
Phillips
,
Farheen N.
Sayed
,
Giulio I.
Lampronti
,
Fabio
Orlandi
,
Pascal
Manuel
,
Iuliia
Mikulska
,
Clare P.
Grey
,
Sian E.
Dutton
Diamond Proposal Number(s):
[34243, 32018]
Open Access
Abstract: NaNiO2 is a promising cathode material for sodium-ion batteries due to its high theoretical capacity of 235.8 mAh.g–1. However, as with many Na-ion cathode materials, a series of poorly understood phase transitions occur on electrochemical cycling, inducing volume mismatch-based stress/strain, resulting in particle cracking, electrochemically disconnected particles and, therefore, irreversible capacity loss. This behavior is one key obstacle to developing long-lasting, high-performance Na-ion batteries. Although the series of phases that form as NaxNiO2 is electrochemically cycled have been previously identified, their structures remained unsolved, limiting our ability to understand and control the phase transition behavior. Here, we report structural solutions based on Rietveld refinement against high-resolution synchrotron x-ray diffraction (SXRD) and neutron powder diffraction (NPD) for the phases obtained on desodiation: P″3-Na1/2NiO2, O″3-Na2/5NiO2, and O‴3-Na1/3NiO2. Each phase contains a unique Na+/vacancy ordering, minimizing intralayer electrostatic repulsions between Na+ ions, and Nix+-charge ordering decreasing interlayer repulsions through the location of lower valence Nix+ nearer to vacancies. Using these structures, we conduct sequential Rietveld refinement against operando SXRD data, which supports prior identification of a transient P‴3-Na1/2<x<2/3NiO2 phase, not isolable ex situ. Operando data also identify the presence of a solid-solution phase O″3δ-Na1/3<x<2/5NiO2 and second-order behavior of the O″3-Na2/5NiO2 → O‴3-Na1/3NiO2 phase transition at the top of charge. This work provides unprecedented insight into structural evolution during electrochemical cycling in Ni-rich Na cathodes (and likely Li analogues), paving the way toward rational doping regimes designed to disrupt degradation-inducing phase transitions, increasing capacity and cycle lifetime, thus improving the performance of Co-free Na and Li cathodes.
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May 2026
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[38563]
Open Access
Abstract: The development of diverse battery chemistries demands advanced diagnostic techniques to study them. Neutron diffraction, which is sensitive to light elements and capable of distinguishing transition metals with similar electronic configurations, is well-suited to probe crystallographic transformations in battery materials and their degradation pathways. Yet its use has been limited by compromised data quality, low time resolution, and the absence of resource-efficient, reproducible, benchmarked electrochemical cells. Here, using the high-resolution cold-neutron diffractometer WISH, we demonstrate operando neutron diffraction studies of standard laboratory-scale single-layer pouch cells without build modifications, electrolyte deuteration, or isotope enrichment of the electrodes, under practical cycling conditions. This expands the battery diagnostic toolkit beyond X-rays and enables academic exploration of both established and emerging technologies, especially lithium–metal, anode-less, and lithium–sulfur batteries.
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Mar 2026
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I06-Nanoscience (XPEEM)
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Purnima P.
Balakrishnan
,
Hemian
Yi
,
Zi-Jie
Yan
,
Wei
Yuan
,
Andreas
Suter
,
Christopher J.
Jensen
,
Pascal
Manuel
,
Fabio
Orlandi
,
Takayasu
Hanashima
,
Christy J.
Kinane
,
Andrew J.
Caruana
,
Dirk
Backes
,
Padraic
Shafer
,
Brian B.
Maranville
,
Zaher
Salman
,
Thomas
Prokscha
,
Cui-Zu
Chang
,
Alexander J.
Grutter
Diamond Proposal Number(s):
[42224]
Abstract: The search for chiral topological superconductivity in magnetic topological insulator (TI)-FeTe heterostructures is a key frontier in condensed matter physics, with potential applications in topological quantum computing. The combination of ferromagnetism, superconductivity, and topologically nontrivial surface states brings together the key elements required for chiral Majorana physics. In this work, we examine the interplay between magnetism and superconductivity at the interfaces between FeTe and a series of Te-based TI overlayers. In both Te/FeTe and superconducting MnBi2Te4/FeTe, any interfacial suppression of antiferromagnetism must affect at most a few nanometers. On the other hand, (Bi,Sb)2Te3/FeTe layers exhibit near-total suppression of antiferromagnetic ordering. Ferromagnetic Cr𝑥(Bi,Sb)2−𝑥Te3 (CBST)/FeTe bilayers exhibit net magnetization in both CBST and FeTe layers, with evidence of interactions between superconductivity and ferromagnetism. These observations identify magnetic TI/FeTe interfaces as an exceptionally robust platform to realize chiral topological superconductivity.
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Oct 2025
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Rebecca
Scatena
,
Alberto
Hernández-Melián
,
Benjamin M.
Huddart
,
Sam
Curley
,
Robert C.
Williams
,
Pascal
Manuel
,
Stephen J.
Blundell
,
Zurab
Guguchia
,
Zachary E.
Manson
,
Jamie L.
Manson
,
G. Timothy
Noe
,
John
Singleton
,
Tom
Lancaster
,
Paul A.
Goddard
,
Roger D.
Johnson
Open Access
Abstract: We present single-crystal neutron diffraction, powder muon spin rotation, and pulsed-field magnetometry measurements on the Heisenberg quantum chiral chain [Cu(pym)(H2O)4]SiF6·H2O (pym = pyrimidine), which displays a fourfold-periodic rotation of the local environment around the Cu(ii) 𝑆=1/2 ions from site to site along the chain. Previous measurements on this material have shown the absence of magnetic order down to surprisingly low temperatures ≥20 mK, as well as the presence of an energy gap for magnetic excitations that grows linearly with magnetic field. Here we find evidence at dilution refrigerator temperatures for a field-induced transition to long-range magnetic order above an applied magnetic field of 3 T. From the polarization of magnetic moments observed with magnetic fields applied in the [−1,2,0] direction, we can identify the static magnetic structure that best accounts for the data. The proposed model is supported microscopically by the presence of an alternating component of the 𝑔 tensor, which produces an internal twofold staggered field that dictates both the direction of the ordered moments and the effective coupling between adjacent chains. The observed magnetic structure is contrary to previous proposals for the departure of the magnitude and field dependence of the energy gap from the predictions of the sine-Gordon model.
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Aug 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893]
Open Access
Abstract: Layered transition metal chalcogenides are a versatile class of compounds that exhibit exotic physical phenomena, including superconductivity, thermoelectric properties and magnetic properties. The magnetic properties of ThCr2Si2-type solid solutions KCo2–xNixCh2 (Ch = S, Se; 0 ≤ x ≤ 2) with metallic properties were probed using magnetometry and powder neutron diffraction (PND). KCo2Se2 is ferromagnetic below ∼90 K and powder neutron diffraction (PND) showed evidence for long-range ferromagnetic order with localized moments of 0.6 μB per cobalt ion. With increasing nickel substitution, the system starts to order antiferromagnetically at x = 0.5. In these cases, PND experiments showed long-range A-type antiferromagnetic order with localized moments of around 1 μB per transition metal at 5 K. The Néel temperature (TN) for three-dimensional long-range ordering exhibits a maximum at x = 1, suggesting that nickel substitution enhances the antiferromagnetic interactions along the stacking direction. Higher nickel content suppresses the magnetic ordering temperature, and KCo0.5Ni1.5Se2 shows no magnetic long-range order with a lack of measurable Bragg peaks by PND (although a magnetic transition is evident by magnetometry), and further increasing the nickel content causes the system to become paramagnetic in the region 1.6 ≤ x ≤ 2. Our results show that increasing the electron count in the KCo2–xNixSe2 series has a dramatic effect on the physical properties. The analogous sulfide series - KCo2–xNixS2─shows similar behavior, and the series CsCo2–xNixSe2, containing a larger alkali metal ion, is comparable apart from the lack of a ferromagnetic region at high Co contents in the absence of an applied magnetic field.
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Jul 2025
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Open Access
Abstract: Due to their potential applications in low-power consumption and/or multistate memory devices, multiferroic materials have attracted a lot of attention in the condensed matter community. As part of the effort to identify new multiferroic compounds, perovskite-based GdCrO3 was studied in both bulk and thin film samples. A strong enhancement of the capacitance in a field suggested ferroelectric behaviour but significant leakage and no well developed P–E hysteresis loops were observed. Measurements clearly indicate the existence of a polar phase but only below 2 K (likely connected to Gd ordering). Here the determination of the magnetic structure through neutron diffraction collected on an isotopic 160GdCrO3 sample at the WISH diffractometer at ISIS is reported. The presence of three successive magnetic phases as a function of temperature (commensurate, spin re-orientation and incommensurate phases once the Gd order), previously only seen by magnetization, is confirmed. Using the most recent guidelines for reporting the determined structures, we highlight the benefits of using such nomenclature for discussing physical properties and consider possible mechanisms and couplings that led this seemingly rather isotropic system to display the complex structures observed.
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Jun 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: The pseudo Ruddlesden–Popper phase Li2CaTa2O7 is converted to ZnCaTa2O7, FeCaTa2O7, or CoCaTa2O7 by reaction with the corresponding transition-metal dichloride. Diffraction data reveal that ZnCaTa2O7 adopts a polar crystal structure (P2cm) with the Zn2+cations ordered into stripes within the interlayer coordination sites, and the TaO6 units adopt an a–b–c+/–(a–b–)c+ tilting pattern. In contrast, FeCaTa2O7 and CoCaTa2O7 adopt polar structures (P21nm) with the transition-metal cations ordered in a checkerboard pattern within the interlayer coordination sites, and the TaO6 units adopt an a–b–c+/ b–a–c+ tilting pattern. The different polar structures adopted are rationalized on the basis of the size of the interlayer transition-metal cation. On cooling, FeCaTa2O7 (TN = 40 K) and CoCaTa2O7 (TN = 25 K) adopt antiferromagnetically ordered states with spins aligned parallel to the crystallographic stacking axis and arranged in a G-type manner. Close inspection of the NPD data collected from FeCaTa2O7 at low temperature reveals a diffuse component to the magnetic scattering, which, in combination with magnetization data, suggest a glassy component to the low-temperature magnetic state. Neither FeCaTa2O7 nor CoCaTa2O7 shows significant lattice parameter anomalies around their respective Néel temperatures, in contrast to the previously reported manganese analogue MnCaTa2O7.
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Jun 2025
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I11-High Resolution Powder Diffraction
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James M. A.
Steele
,
Annalena R.
Genreith-Schriever
,
Joshua D.
Bocarsly
,
Liam A. V.
Nagle-Cocco
,
Farheen N.
Sayed
,
Marie
Juramy
,
Christopher A.
O'Keefe
,
Fabio
Orlandi
,
Pascal
Manuel
,
Sian E.
Dutton
,
Clare P.
Grey
Diamond Proposal Number(s):
[34243]
Open Access
Abstract: NaNiO2 (NNO) has been investigated as a promising sodium-ion battery cathode material, but it is limited by degradation-induced capacity fade. On desodiation, NNO forms multiple phases with large superstructures due in part to Na+-ion vacancy ordering; however, their structures are unknown. Here, we report a structural solution to the Na2/3NiO2 (P′3) desodiated phase using combined Rietveld refinement of high-resolution synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) data, magnetic susceptibility, and 23Na solid-state nuclear magnetic resonance (ssNMR) spectroscopy. Our experimental results are compared to ab initio molecular dynamics (AIMD) simulations, which indicate multiple low-energy structures that are dynamically populated. We observe a combination of competing effects that contribute to the resultant dynamic nature of the structure, including honeycomb ordering of mixed-valence Ni, orbital ordering of Jahn–Teller (JT) distorted Ni3+, and zigzag Na+/vacancy ordering. Our work provides evidence of multiple contributions to the structures of desodiated Na2/3NiO2, along with a framework for investigating the other unsolved desodiated structures. This work may also inform our understanding of the Jahn–Teller evolution in other nickel-rich lithium- and sodium-ion cathodes, such as LiNiO2.
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Mar 2025
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Abstract: Through a combination of magnetic susceptibility, specific heat, and neutron powder diffraction measurements we have revealed a sequence of four magnetic phase transitions in the columnar quadruple perovskite Er2CuMnMn4O12. A key feature of the quadruple perovskite structural framework is the complex interplay of multiple magnetic sublattices via frustrated exchange topologies and competing magnetic anisotropies. It is shown that in Er2CuMnMn4O12, this phenomenology gives rise to multiple spin-reorientation transitions driven by the competition of easy-axis single ion anisotropy and the Dzyaloshinskii–Moriya interaction; both within the manganese B-site sublattice. At low temperature, one Er sublattice orders due to a finite f-d exchange field aligned parallel to its Ising axis, while the other Er sublattice remains non-magnetic until a final, symmetry-breaking phase transition into the ground state. This non-trivial low-temperature interplay of transition metal and rare-earth sublattices, as well as an observed k = (0, 0, ½) periodicity in both manganese spin canting and Er ordering, raises future challenges to develop a complete understanding of the R2CuMnMn4O12 family.
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Dec 2024
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