I21-Resonant Inelastic X-ray Scattering (RIXS)
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Xunyang
Hong
,
Yuetong
Wu
,
Izabela
Bialo
,
Ying
Chan
,
Sze Tung
Li
,
Leonardo
Martinelli
,
Orion
Gerguri
,
Annabella
Drewanowski
,
Qiang
Gao
,
Xiaolin
Ren
,
Xingjiang
Zhou
,
Zhihai
Zhu
,
Alice
Galdi
,
Darrell G.
Schlom
,
Kyle M.
Shen
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Nicholas B.
Brookes
,
Henrikm.
Ronnow
,
Qisi
Wang
,
Johan
Chang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Optimization of unconventional superconductivity involves a balance of interaction strengths. Precise determination of correlation strength across different material families is therefore important. Here, we present a combined X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) study of infinite-layer PrNiO2 and SrCuO2 that enables fair comparison of their interaction strengths. For both compounds, we study the orbital and magnetic excitations and extract their dispersions along high-symmetry directions. Using a single-band Hubbard model and including physically plausible assumptions about higher-order exchange interactions, we estimate the correlation factor U/t for both compounds. A key finding is that despite the prediction of a smaller Coulomb repulsion U, PrNiO2 exhibits a correlation strength U/t that is 20% stronger than that of its isostructural cuprate counterpart SrCuO2. This indicates that moderation of the correlation strength may further optimize superconductivity in nickelates.
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May 2026
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I06-Nanoscience (XPEEM)
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Diamond Proposal Number(s):
[31889]
Abstract: Rare-earth iron garnet (RE3Fe5O12) films are promising insulating ferrimagnets. They can show low magnetic damping, perpendicular magnetic anisotropy, and ultrafast spin dynamics, which makes them ideal for spin transport applications. In this work, we investigate the interaction between the magnetic sublattices in Er3Fe5O12 thin films grown by pulsed laser deposition on a Gd3Ga5O12 substrate. Structural and magnetic characterization reveals high-quality single-crystal growth, with a compensation temperature close to the reported bulk value (∼80 K). Magnetic phase diagrams based on element-specific measurements map out the regions where ferrimagnetic, canted, and aligned phases are stable across the compensation temperature. The micromagnetic dynamics resulting from perpendicular magnetic pulse perturbation of an in-plane magnetized layer was investigated at room temperature and revealed complex configurations. These results are key features for modulating magnetization dynamics through the compensation phenomenon, which is essential for spin-based devices operating in a low-temperature regime.
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Mar 2026
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I05-ARPES
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I.
Biało
,
Qisi
Wang
,
J.
Küspert
,
X.
Hong
,
L.
Martinelli
,
O.
Gerguri
,
Y.
Chan
,
K.
Von Arx
,
O. K.
Forslund
,
W. R.
Pudełko
,
C.
Lin
,
N. C.
Plumb
,
Y.
Sassa
,
D.
Betto
,
N. B.
Brookes
,
M.
Rosmus
,
N.
Olszowska
,
Ma. D.
Watson
,
T. K.
Kim
,
C.
Cacho
,
M.
Horio
,
M.
Ishikado
,
H. M.
Rønnow
,
J.
Chang
Diamond Proposal Number(s):
[32147]
Open Access
Abstract: Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of these interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compounds with the highest superconducting onset temperature. To fill this gap, we introduce a pristine, half-filled thallium-based cuprate system, Tl2Ba5Cu4Ox. Using high-resolution resonant inelastic x-ray scattering, we probe long-lived magnon excitations and uncover a pronounced kink in the magnon dispersion, marked by a simultaneous change in group velocity and lifetime broadening. Modeling the dispersion within a Hubbard-Heisenberg approach, we extract the interaction strength and compare it with other cuprate systems. Our results establish a cuprate universal relation between electron-electron interaction and magnon zone-boundary dispersion. Superconductivity seems to be optimal at intermediate correlation strength, suggesting an optimal balance between localization and itinerancy.
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Dec 2025
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Maryia
Zinouyeva
,
Martina
Fracchia
,
Giulia
Maranini
,
Davide
Impelluso
,
Nicholas B.
Brookes
,
Lorenzo
Grilli
,
Kurt
Kummer
,
Francesco
Rosa
,
Matteo
Aramini
,
Giacomo
Ghiringhelli
,
Paolo
Ghigna
,
Marco
Moretti Sala
,
Mauro
Coduri
Open Access
Abstract: We employ several X-ray based techniques, including X-ray diffraction, X-ray absorption spectroscopy and resonant inelastic X-ray scattering, to disentangle the contributions of individual chemical species to the structural, electronic and magnetic properties of high-entropy oxides. In the benchmark compound Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O and related systems, we unambiguously resolve a sizable Jahn–Teller distortion at the Cu sites, more pronounced in the absence of Ni2+ and Mg2+, suggesting that these ions promote positional order, whereas Cu2+ ions act to destabilize it. Moreover, we detect magnetic excitations and estimate the strength of the interactions between pairs of different magnetic elements. Our results provide valuable insights into the role of various chemical species in shaping the physical properties of high-entropy oxides.
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Nov 2025
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Open Access
Abstract: Multi-walled carbon nanotubes (MWCNTs), synthesized using the microwave plasma-enhanced chemical vapor deposition (MPCVD) technique, have been examined to elucidate their electronic and magnetic structures through near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. NEXAFS analysis at the Fe and Co L-edges reveals the presence of Fe-metal nanoparticles embedded within the CNT lattice, along with divalent Co ions coordinated to the matrix in an octahedral symmetry. Furthermore, the appearance of two distinct NEXAFS peaks between the π* and σ* transitions indicates 1s to sp3 hybridization, attributed to the interaction of Fe and Co2+ ions with the carbon nanotube structure. Additionally, XMCD spectra confirm that MWCNTs exhibit room temperature ferromagnetism, primarily driven by Fe–C and Co–C bonding within the nanotubes. This intrinsic ferromagnetic behavior, along with the high aspect ratio and unique electronic properties of MWCNTs, highlights their promising potential for applications in spintronic storage devices.
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Mar 2025
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Teguh Citra
Asmara
,
Robert J.
Green
,
Andreas
Suter
,
Yuan
Wei
,
Wenliang
Zhang
,
Daniel
Knez
,
Grant
Harris
,
Yi
Tseng
,
Tianlun
Yu
,
Davide
Betto
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Yannick Maximilian
Klein
,
Neeraj
Kumar
,
Carlos W.
Galdino
,
Zaher
Salman
,
Thomas
Prokscha
,
Marisa
Medarde
,
Elisabeth
Müller
,
Yona
Soh
,
Nicholas B.
Brookes
,
Ke-Jin
Zhou
,
Milan
Radovic
,
Thorsten
Schmitt
Diamond Proposal Number(s):
[28665]
Open Access
Abstract: Strongly-correlated transition-metal oxides are widely known for their various exotic phenomena. This is exemplified by rare-earth nickelates such as LaNiO3, which possess intimate interconnections between their electronic, spin, and lattice degrees of freedom. Their properties can be further enhanced by pairing them in hybrid heterostructures, which can lead to hidden phases and emergent phenomena. An important example is the LaNiO3/LaTiO3 superlattice, where an interlayer electron transfer has been observed from LaTiO3 into LaNiO3 leading to a high-spin state. However, macroscopic emergence of magnetic order associated with this high-spin state has so far not been observed. Here, by using muon spin rotation, x-ray absorption, and resonant inelastic x-ray scattering, direct evidence of an emergent antiferromagnetic order with high magnon energy and exchange interactions at the LaNiO3/LaTiO3 interface is presented. As the magnetism is purely interfacial, a single LaNiO3/LaTiO3 interface can essentially behave as an atomically thin strongly-correlated quasi-2D antiferromagnet, potentially allowing its technological utilization in advanced spintronic devices. Furthermore, its strong quasi-2D magnetic correlations, orbitally-polarized planar ligand holes, and layered superlattice design make its electronic, magnetic, and lattice configurations resemble the precursor states of superconducting cuprates and nickelates, but with an S→1 spin state instead.
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Aug 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Izabela
Bialo
,
Leonardo
Martinelli
,
Gabriele
De Luca
,
Paul
Worm
,
Annabella
Drewanowski
,
Simon
Jöhr
,
Jaewon
Choi
,
Mirian
Garcia-Fernandez
,
Stefano
Agrestini
,
Ke-Jin
Zhou
,
Kurt
Kummer
,
Nicholas B.
Brookes
,
Luo
Guo
,
Anthony
Edgeton
,
Chang B.
Eom
,
Jan M.
Tomczak
,
Karsten
Held
,
Marta
Gibert
,
Qisi
Wang
,
Johan
Chang
Diamond Proposal Number(s):
[30189]
Open Access
Abstract: Magnetic frustration is a route for novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either lattice geometry or incompatible exchange interactions. Here, we find that epitaxial strain is an effective tool for tuning antiferromagnetic exchange interactions in a square-lattice system. By studying the magnon excitations in La2NiO4 films using resonant inelastic x-ray scattering, we show that the magnon displays substantial dispersion along the antiferromagnetic zone boundary, at energies that depend on the lattice of the film’s substrate. Using first principles simulations and an effective spin model, we demonstrate that the antiferromagnetic next-nearest neighbour coupling is a consequence of the two-orbital nature of La2NiO4. Altogether, we illustrate that compressive epitaxial strain enhances this coupling and, as a result, increases the level of incompatibility between exchange interactions within a model square-lattice system.
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Jul 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Subhrangsu
Sarkar
,
Roxana
Capu
,
Yurii G
Pashkevich
,
Jonas
Knobel
,
Marli R.
Cantarino
,
Abhishek
Nag
,
Kurt
Kummer
,
Davide
Betto
,
Roberto
Sant
,
Christopher W.
Nicholson
,
Jarji
Khmaladze
,
Ke-Jin
Zhou
,
Nicholas B.
Brookes
,
Claude
Monney
,
Christian
Bernhard
Diamond Proposal Number(s):
[22149]
Open Access
Abstract: Heterostructures from complex oxides allow one to combine various electronic and magnetic orders as to induce new quantum states. A prominent example is the coupling between superconducting and magnetic orders in multilayers from high-Tc cuprates and manganites. A key role is played here by the interfacial CuO2 layer whose distinct properties remain to be fully understood. Here, we study with resonant inelastic X-ray scattering (RIXS) the magnon excitations of this interfacial CuO2 layer. In particular, we show that the underlying antiferromagnetic exchange interaction at the interface is strongly suppressed to J ≈ 70 meV, as compared to J ≈ 130 meV for the CuO2 layers away from the interface. Moreover, we observe an anomalous momentum dependence of the intensity of the interfacial magnon mode and show that it suggests that the antiferromagnetic order is accompanied by a particular kind of orbital order that yields a so-called altermagnetic state. Such a two-dimensional altermagnet has recently been predicted to enable new spintronic applications and superconducting proximity effects.
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Mar 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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K.
Scott
,
E.
Kisiel
,
F.
Yakhou
,
S.
Agrestini
,
Mirian
Garcia-Fernandez
,
K.
Kummer
,
J.
Choi
,
R. D.
Zhong
,
J. A.
Schneeloch
,
G. D.
Gu
,
Ke-Jin
Zhou
,
N. B.
Brookes
,
A. F.
Kemper
,
M.
Minola
,
F.
Boschini
,
A.
Frano
,
A.
Gozar
,
E. H.
Da Silva Neto
Diamond Proposal Number(s):
[28523, 30146]
Abstract: Recent improvements in the energy resolution of resonant inelastic x-ray scattering experiments (RIXS) at the Cu-
L
3
edge have enabled the study of lattice, spin, and charge excitations. Here, we report on the detection of a low-intensity signal at 140 meV, twice the energy of the bond-stretching (BS) phonon mode, in the cuprate superconductor
Bi
2
Sr
2
Ca
Cu
2
O
8
+
x
(Bi-2212). Ultrahigh-resolution polarimetric RIXS measurements allow us to resolve the outgoing polarization of the signal and identify this feature as a two-phonon excitation. Further, we study the connection between the two-phonon mode and the BS one-phonon mode by constructing a joint density of states toy model that reproduces the key features of the data.
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Mar 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Leonardo
Martinelli
,
Krzysztof
Wohlfeld
,
Jonathan
Pelliciari
,
Riccardo
Arpaia
,
Nicholas B.
Brookes
,
Daniele
Di Castro
,
Mirian
Garcia-Fernandez
,
Mingu
Kang
,
Yoshiharu
Krockenberger
,
Kurt
Kummer
,
Daniel E.
Mcnally
,
Eugenio
Paris
,
Thorsten
Schmitt
,
Hideki
Yamamoto
,
Andrew
Walters
,
Ke-Jin
Zhou
,
Lucio
Braicovich
,
Riccardo
Comin
,
Marco
Moretti Sala
,
Thomas P.
Devereaux
,
Maria
Daghofer
,
Giacomo
Ghiringhelli
Diamond Proposal Number(s):
[20690]
Abstract: We have investigated the
3
d
orbital excitations in
CaCuO
2
(CCO),
Nd
2
CuO
4
(NCO), and
La
2
CuO
4
(LCO) using high-resolution resonant inelastic x-ray scattering. In LCO they behave as well-localized excitations, similarly to several other cuprates. On the contrary, in CCO and NCO the
d
x
y
orbital clearly disperses, pointing to a collective character of this excitation (orbiton) in compounds without apical oxygen. We ascribe the origin of the dispersion as stemming from a substantial next-nearest-neighbor (NNN) orbital superexchange. Such an exchange leads to the liberation of the orbiton from its coupling to magnons, which is associated with the orbiton hopping between nearest neighbor copper sites. Finally, we show that the exceptionally large NNN orbital superexchange can be traced back to the absence of apical oxygens suppressing the charge transfer energy.
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Feb 2024
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