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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B22-Multimode InfraRed imaging And Microspectroscopy
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Dukula
De Alwis Jayasinghe
,
Yinlin
Chen
,
Jiangnan
Li
,
Justyna M.
Rogacka
,
Meredydd
Kippax-Jones
,
Wanpeng
Lu
,
Sergey
Sapchenko
,
Jinyue
Yang
,
Sarayute
Chansai
,
Tianze
Zhou
,
Lixia
Guo
,
Yujie
Ma
,
Longzhang
Dong
,
Daniil
Polyukhov
,
Lutong
Shan
,
Yu
Han
,
Danielle
Crawshaw
,
Xiangdi
Zeng
,
Zhaodong
Zhu
,
Lewis
Hughes
,
Mark D.
Frogley
,
Pascal
Manuel
,
Svemir
Rudic
,
Yongqiang
Chen
,
Christopher
Hardacre
,
Martin
Schroeder
,
Sihai
Yang
Open Access
Abstract: Ammonia (NH3) production in 2023 reached 150 million tons and is associated with potential concomitant production of up to 500 million tons of CO2 each year. Efforts to produce green NH3 are compromised since it is difficult to separate using conventional condensation chillers, but in situ separation with minimal cooling is challenging. While metal–organic framework materials offer some potential, they are often unstable and decompose in the presence of caustic and corrosive NH3. Here, we address these challenges by developing a pore-expansion strategy utilizing the flexible phosphonate framework, STA-12(Ni), which shows exceptional stability and capture of NH3 at ppm levels at elevated temperatures (100–220 °C) even under humid conditions. A remarkable NH3 uptake of 4.76 mmol g–1 at 100 μbar (equivalent to 100 ppm) is observed, and in situ neutron powder diffraction, inelastic neutron scattering, and infrared microspectroscopy, coupled with modeling, reveal a pore expansion from triclinic to a rhombohedral structure on cooperative binding of NH3 to unsaturated Ni(II) sites and phosphonate groups. STA-12(Ni) can be readily engineered into pellets or monoliths without losing adsorption capacity, underscoring its practical potential.
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Nov 2024
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B22-Multimode InfraRed imaging And Microspectroscopy
I11-High Resolution Powder Diffraction
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Yu
Han
,
Wenyuan
Huang
,
Meng
He
,
Bing
An
,
Yinlin
Chen
,
Xue
Han
,
Lan
An
,
Meredydd
Kippax-Jones
,
Jiangnan
Li
,
Yuhang
Yang
,
Mark D.
Frogley
,
Cheng
Li
,
Danielle
Crawshaw
,
Pascal
Manuel
,
Svemir
Rudic
,
Yongqiang
Chen
,
Ian
Silverwood
,
Luke L.
Daemen
,
Anibal J.
Ramirez-Cuesta
,
Sarah J.
Day
,
Stephen P.
Thompson
,
Ben F.
Spencer
,
Marek
Nikiel
,
Daniel
Lee
,
Martin
Schroeder
,
Sihai
Yang
Diamond Proposal Number(s):
[37155, 36474]
Open Access
Abstract: Capture of trace benzene is an important and challenging task. Metal–organic framework materials are promising sorbents for a variety of gases, but their limited capacity towards benzene at low concentration remains unresolved. Here we report the adsorption of trace benzene by decorating a structural defect in MIL-125-defect with single-atom metal centres to afford MIL-125-X (X = Mn, Fe, Co, Ni, Cu, Zn; MIL-125, Ti8O8(OH)4(BDC)6 where H2BDC is 1,4-benzenedicarboxylic acid). At 298 K, MIL-125-Zn exhibits a benzene uptake of 7.63 mmol g−1 at 1.2 mbar and 5.33 mmol g−1 at 0.12 mbar, and breakthrough experiments confirm the removal of trace benzene (from 5 to <0.5 ppm) from air (up to 111,000 min g−1 of metal–organic framework), even after exposure to moisture. The binding of benzene to the defect and open Zn(II) sites at low pressure has been visualized by diffraction, scattering and spectroscopy. This work highlights the importance of fine-tuning pore chemistry for designing adsorbents for the removal of air pollutants.
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Nov 2024
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[31308]
Open Access
Abstract: Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model.
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Nov 2024
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