I06-Nanoscience (XPEEM)
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Weican
Lan
,
Chaocheng
Liu
,
Yajuan
Feng
,
Ruiqi
Liu
,
Yafei
Chu
,
Lu
Cheng
,
Chao
Wang
,
Huijuan
Wang
,
Minghui
Fan
,
Zixun
Zhang
,
Yuran
Niu
,
Jheng-Cyuan
Lin
,
Francesco
Maccherozzi
,
Hengli
Duan
,
Wensheng
Yan
Diamond Proposal Number(s):
[40612]
Abstract: Excitons are primary elementary excitations in solids that present both fundamental interest and technological importance, showing great potential for photospintronic and quantum transduction applications. The emerging coherent collective excitations in two-dimensional antiferromagnetic semiconductors raise prospects for spin-exciton interactions and multifield control schemes. However, realizing the arbitrary manipulation of excitonic quantum states, while preserving the inherent dynamic and response advantages of antiferromagnetic nature remains challenging. Here we achieve bidirectional modulation of the CrSBr exciton energy via interfacial interaction-modified spin-exciton coupling in a CrSBr/Fe3GaTe2 heterostructure. Compared with pristine CrSBr, the photoluminescence peaks in the heterostructure can exhibit blueshift and redshift corresponding to 6.1% and 8.6% of the total bandwidth, respectively. We reveal that the interfacial charge-transfer-driven magnetic coupling in the heterostructure effectively enhances the magnetic anisotropy and the exchange interaction of CrSBr, thereby stabilizing its antiferromagnetic spin configuration, suppressing interlayer electron-hole recombination, and ultimately leading to an anomalous blueshift of the exciton emission. Our findings demonstrate an approach for bidirectionally modulating exciton energy in two-dimensional antiferromagnetic semiconductors, which provides substantial flexibility in device design and offers an avenue for potential wavelength control in quantum information and optoelectronic technologies.
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Feb 2026
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893, 14239]
Open Access
Abstract: Fluorination of the n = 2 Ruddlesden–Popper oxide, La3Ni2O7, with polyvinylidene fluoride yields La3Ni2O5F4, a phase in which fluoride ions have been inserted into interstitial sites in the Ruddlesden–Popper framework and also exchanged with the oxide ions residing on apical anion sites. Reaction with LiH at 190 °C reduces La3Ni2O5F4 by extracting interstitial fluoride ions. The resulting phase, La3Ni2O5F3, adopts a structure described in space group Pbcm in which the fluoride ions in the half-filled interstitial layer are arranged in chains parallel to the y-axis, and the NiO5F octahedra adopt an a–a–c+/–(a–a–)c+ tilting pattern. Further reduction with LiH at 250 °C converts La3Ni2O5F3 into La3Ni2O5F, a Ni1+ phase which adopts a T′-structure consisting of double infinite-sheets of apex linked NiO4 squares, stacked with LaOF fluorite-type layers. Magnetization and neutron diffraction data indicate La3Ni2O5F3 adopts an antiferromagnetically ordered state below TN = 225 K, while magnetization data from La3Ni2O5F exhibit a broad maximum centered at 75 K, suggestive of antiferromagnetic order.
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Feb 2026
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893]
Open Access
Abstract: The crystal and magnetic structures of Sr3Fe4O6S2 (= Sr3Fe2O5Fe2OS2) and Sr4Fe4O7S2 (= Sr4Fe2O6Fe2OS2), designed using a building-block approach, are reported. They are fully charge-ordered with Fe2+ and Fe3+ ions in distinct layers showing independent long-range magnetic order. Complex microstructures in some regions suggest new targets.
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Feb 2026
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Emily C.
Mcfarlane
,
Antonio
Sanna
,
Matthew J.
Gilbert
,
Jonas A.
Krieger
,
Mihir
Date
,
Gabriele
Domaine
,
Banabir
Pal
,
Anirban
Chakraborty
,
Pranava K.
Sivakumar
,
Procopios C.
Constantinou
,
Anna
Hartl
,
Enrico G.
Della Valle
,
Camilla
Pellegrini
,
Vladimir N.
Strocov
,
Stuart S. P.
Parkin
,
Niels B. M.
Schroeter
Open Access
Abstract: Superconductivity in the transition-metal dichalcogenide PdTe2 has been attributed to the proximity of a three-dimensional Van Hove singularity to the Fermi level. In isostructural NiTe2, recently used as the weak link in a Josephson diode, a similar Van Hove singularity has been predicted to occur, but superconductivity is mysteriously absent. Using bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy, we reveal that this Van Hove singularity lies even closer to the Fermi level in NiTe2 than in PdTe2. To explain the lack of superconductivity in NiTe2, we perform ab initio calculations incorporating the Kukkonen Overhauser interaction, showing that an incipient magnetic instability suppresses superconductivity at an unprecedented scale. Finally, we present a tight-binding model that links the Van Hove singularity to a sign change in the Josephson diode effect at small magnetic fields, suggesting a new mechanism for Josephson diodes.
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Feb 2026
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I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[35696]
Open Access
Abstract: Cobalt ferrite nanoparticles are a benchmark among low-to-medium energy alternatives to rare-earth permanent magnets, although their intrinsic behavior is often obscured by surface disorder, finite-size effects, and superparamagnetic relaxation. Here, we overcome these limitations by synthesizing large, highly crystalline cobalt-doped ferrite nanoparticles (≈ 25 nm), which remain blocked at room temperature and thus provide a clean platform to disentangle the fundamental role of cobalt in the spinel lattice. By systematically varying the cobalt content, we reveal a complex interplay between cation distribution, oxygen vacancy formation, and magnetic response. Structural and compositional analysis confirms predominant Co2+ occupancy at octahedral sites, accompanied by a redistribution of Fe2+/Fe3+ and non-linear oxygen vacancy generation. We find that while saturation magnetization is largely governed by defect chemistry, the coercivity and effective anisotropy are primarily controlled by cobalt incorporation and saturate at intermediate compositions. In contrast, thermomagnetic analysis reveals an anomalous evolution of magnetization at intermediate temperatures for specific cobalt contents. This behavior is consistent with a change in the anisotropy landscape, suggestive of a growing contribution from higher-order anisotropy terms, rather than a simple uniform increase in magnetocrystalline anisotropy. These results indicate that cobalt doping tunes the balance between different anisotropy contributions in a composition- and temperature-dependent manner. Overall, our findings highlight the subtle interplay between cation distribution, anisotropy landscape, and thermal stability in spinel ferrites, providing fundamental insight for the design of high-coercivity rare-earth-free nanomagnets.
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Feb 2026
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I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[36197]
Abstract: Heterostructures composed of heavy metal and van der Waals (vdW) magnets serve as platforms to investigate magnetotransport properties, enabling the electric readout of the spin-flop transition in the vdW antiferromagnet. We investigate the spin and orbital contributions to magnetism in Pt/exfoliated multilayer CrPS4 heterostructure using the synchrotron-radiation based x-ray magnetic circular dichroism technique measured in the total electron yield (TEY) mode. The TEY detection, with probing depth of 5–10 nm, mainly reflects the interfacial magnetic behavior near the Pt/CrPS4 boundary. A spin-flop transition appears near 0.7 T in both the CrPS4 single crystal and the Pt/CrPS4 heterostructures. The total Cr moment remains ∼2 μB/f.u. in both systems at 14 T and 6 K. In Pt/CrPS4, the orbital moment is strongly modulated by Pt, as manifested in the enhancement from ∼0.1 μB/f.u. in CrPS4 to ∼0.5 μB/f.u. in Pt/CrPS4, an effect attributable to the strong spin–orbit coupling with Pt. At 25 K, the total Cr moment reduces to ∼1.1 μB/f.u. in both systems. The Cr orbital moment in CrPS4 remains low ∼0.1 μB/f.u., whereas in Pt/CrPS4 it remains high ∼0.5 μB/f.u. These findings provide qualitative evidence of robust spin–orbit coupling and orbital hybridization at Pt/CrPS4 interface, and highlight the potential of heavy metal/vdW antiferromagnet heterostructures for spin-orbitronic device applications.
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Feb 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Abstract: Understanding the interplay between electronic, magnetic, and lattice degrees of freedom is essential for advancing two-dimensional (2D) van der Waals magnetic ma- terials toward next-generation spintronic and quantum technologies. The magnetic ordering of 2D magnetic compounds is often related to the electronic structure param- eters, such as spin orbit coupling, Hund’s coupling (JH ), p − d covalency, and inter- orbital Coulomb interactions. Accurately determining such parameters is paramount for understanding the physics of these compounds. This thesis presents a compre- hensive study of the electronic structure and low-energy excitations in 2D magnetic material families CrX3 (X = Cl, Br, and I), VX3 (X = Br and I), and CrSBr, using a combination of synchrotron based x-ray absorption spectroscopy, resonant inelas- tic x-ray scattering (RIXS), and state-of-the-art theoretical modeling, together with atomic multiplet simulations.
High-resolution Cr L3−edge RIXS measurements on CrX3 enabled the first clear
experimental energy separation between spin-allowed quartet states and spin-forbidden
doublet states, which increases upon going from CrCl3 to CrI3. The refined crystal-
field and Racah parameters revealed systematic trends in ligand-field strength and
covalency from Cr to I. The RIXS measurements on VX3 revealed a sign opposition
relation between the trigonal distortion parameters ∆ , hence an e′2 ground state in D3d g
VBr and an e′1a1 ground state in VI , consistent with trigonal elongation and com- 3g1g 3
pression, respectively. Momentum-resolved RIXS measurements on CrSBr revealed dispersing multi-phonons along the crystallographic a axis, and only one phonon mode along the b axis, consistent with its quasi-1D behavior. These findings significantly advance fundamental understanding of vdW magnets and provide a strong foundation for future exploration of their potential in spintronics, optoelectronics, and quantum information technologies.
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Feb 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Marli R.
Cantarino
,
Rafael M. P.
Teixeira
,
Kevin R.
Pakuszewski
,
Wagner R.
Da Silva Neto
,
Juliana G.
De Abrantes
,
Mirian
Garcia-Fernandez
,
Pascoal G.
Pagliuso
,
Cris
Adriano
,
Claude
Monney
,
Thorsten
Schmitt
,
Eric C.
Andrade
,
Fernando A.
Garcia
Diamond Proposal Number(s):
[33194]
Open Access
Abstract: In doped Hund's metals, such as the iron-based superconductors, effects like charge doping and chemical pressure are often considered the dominant factors. Partial chemical substitution, however, inevitably introduces disorder. Here, we investigate spin excitations in Ba(Fe1−𝑥Cr𝑥)2As2 (CrBFA) by high-resolution resonant inelastic x-ray scattering for samples with 𝑥=0,0.035, and 0.085. In CrBFA, Cr acts as a hole dopant, but also introduces localized spins that compete with Fe-derived magnetic excitations. We found that the Fe-derived magnetic excitations are softened and damped, becoming overdamped for 𝑥=0.085. At this doping level, complementary angle-resolved photoemission spectroscopy measurements show increased electronic localization and a suppression of the nematic 𝑑𝑥𝑧/𝑑𝑦𝑧 band splitting present in the parent compound. We thus propose a localized spin model that explicitly incorporates substitutional disorder and Cr local moments, successfully reproducing our key observations. Our findings reveal a case where disorder dominates over charge doping in the case of a Hund's metal.
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Feb 2026
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I16-Materials and Magnetism
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Connor A.
Occhialini
,
Christie
Nelson
,
Alessandro
Bombardi
,
Shiyu
Fan
,
Raul
Acevedo-Esteves
,
Riccardo
Comin
,
Dmitri N.
Basov
,
Maki
Musashi
,
Masashi
Kawasaki
,
Masaki
Uchida
,
Hoydoo
You
,
John F.
Mitchell
,
Valentina
Bisogni
,
Claudio
Mazzoli
,
Jonathan
Pelliciari
Diamond Proposal Number(s):
[40048]
Abstract: We report Ru 𝐿3-edge resonant X-ray diffraction studies on single-crystal and (001)-oriented epitaxial films of RuO2. We investigate the distinct 𝐐=(100) and (001) Bragg-forbidden reflections as a function of incident energy, azimuthal angle, and temperature. The results show that the observed resonant diffraction in RuO2 is fully consistent with a resonant charge anisotropy signal of structural origin permitted by the parent (nonmagnetic) rutile 𝑃42/𝑚𝑛𝑚 space group. These results significantly constrain the magnetic contribution to the resonant diffraction signal and indicate the unlikely existence of 𝐤=0 antiferromagnetic order in RuO2.
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Feb 2026
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E02-JEM ARM 300CF
I05-ARPES
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Amy
Carl
,
Nicholas
Clark
,
David G.
Hopkinson
,
Matthew
Hamer
,
Matthew
Watson
,
Laxman
Nagireddy
,
James E.
Nunn
,
Alexei
Barinov
,
Yichao
Zou
,
William
Thornley
,
Casey
Cheung
,
Wendong
Wang
,
Sam
Sullivan-Allsop
,
Xiao
Li
,
Astrid
Weston
,
Eli G.
Castanon
,
Andrey V.
Kretinin
,
Cephise
Cacho
,
Neil R.
Wilson
,
Sarah J.
Haigh
,
Roman
Gorbachev
Diamond Proposal Number(s):
[21597, 21981, 24290, 24338]
Open Access
Abstract: Magnetic two-dimensional materials are a promising platform for novel nano-electronic device architectures. One such layered crystal is the ferromagnetic semiconductor chromium germanium telluride (Cr2Ge2Te6) which recently attracted interest due to its potential for spintronics and memory applications. Here we investigate its properties from the structural standpoint using atomic resolution Scanning Transmission Electron Microscopy (STEM) and present the first atomic resolution images down to its monolayer limit. We develop a novel technique that allows one to map the local tilt with unprecedented spatial resolution using only high-resolution images, enabling mapping of the topography and morphological variation of atomically thin crystals. Using it, we show that the Cr2Ge2Te6 monolayer has an unusually large out-of-plane rippling, with local tilt variation reaching 20° over few nm length scales. We hypothesize that such a strongly buckled structure originates from both point and extended lattice defects which are more prevalent in monolayer crystals. In addition, we correlate the structural observations with the band structure measurements using Angle-Resolved Photoemission Spectroscopy (ARPES). We believe that both the atomic scale insights we have gained on Cr2Ge2Te6 and our novel approach to nanoscale topography mapping will benefit the development of van der Waals heterostructures in both fundamental and applied research.
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Feb 2026
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