B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Ellen M.
Kiens
,
Ester
Pérez-Penco
,
Iris C. G.
Van Den Bosch
,
Silvia
Mauri
,
Emma
Van Der Minne
,
Matthijs A.
Van Spronsen
,
Frank
De Groot
,
Guido
Mul
,
Gertjan
Koster
,
Piero
Torelli
,
Roland
Bliem
,
Bastian
Mei
,
Christoph
Baeumer
Diamond Proposal Number(s):
[33107, 31118]
Abstract: Perovskite oxides are a versatile class of materials with tunable electronic structures, making them attractive for catalytic applications, including the oxygen evolution reaction (OER). The surface reactivity of these oxides is closely tied to the electronic structure of transition metal cations, particularly their 3d orbital occupation, which can be modulated by interfacial engineering. In this work, we investigate how subsurface engineering influences the interaction of ultrathin LaCoO3 films with water vapor. Using (near) ambient pressure core-level spectroscopy, we observe distinct differences in hydroxyl affinity and Co valence response depending on the electronic structure imposed by the underlying layer. Ultrathin LaCoO3 films with a higher initial Co oxidation state show stronger hydroxyl affinity, while those with a lower Co valence show more significant electronic changes upon water exposure. Our findings demonstrate a form of “remote control” in surface chemistry, where subsurface electronic engineering dictates hydroxyl affinity and electronic response at the surface. This concept offers a new degree of freedom to optimize oxide–adsorbate interactions for (electro)catalysis.
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Apr 2026
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Emma
Van Der Minne
,
Priscila
Vensaus
,
Vadim
Ratovskii
,
Seenivasan
Hariharan
,
Jan
Behrends
,
Cesare
Franchini
,
Jonas
Fransson
,
Sarnjeet S.
Dhesi
,
Felix
Gunkel
,
Florian
Gossing
,
Georgios
Katsoukis
,
Ulrike I.
Kramm
,
Magalí
Lingenfelder
,
Qianqian
Lan
,
Yury V.
Kolen'Ko
,
Yang
Li
,
Ramsundar Rani
Mohan
,
Jeffrey
Mccord
,
Lingmei
Ni
,
Eva
Pavarini
,
Rossitza
Pentcheva
,
David H.
Waldeck
,
Michael
Verhage
,
Anke
Yu
,
Zhichuan J.
Xu
,
Piero
Torelli
,
Silvia
Mauri
,
Narcis
Avarvari
,
Anja
Bieberle-Hütter
,
Christoph
Baeumer
Open Access
Abstract: A central challenge in water electrolysis lies with the oxygen evolution reaction (OER) where the formation of molecular oxygen (O2) is hindered by the constraint of angular momentum conservation. While the reactants OH− or H2O are diamagnetic (DM), the O2 product has a paramagnetic (PM) triplet ground state, requiring a change in spin configuration when being formed. This constraint has prompted interest in spin-selective catalysts as a means to facilitate OER. In this context, the roles of magnetism and chirality-induced spin selectivity (CISS) in promoting the OER reaction have recently been investigated through both theoretical and experimental studies. However, pinpointing the key principles and their relative contribution in mediating spin-enhancement remains a significant challenge. This roadmap offers a forward-looking perspective on current experimental trends and theoretical developments in spin-enhanced OER electrocatalysis and outlines strategic directions for integrating incisive experiments and operando approaches with computational modeling to disentangle key mechanisms. By providing a conceptual framework and identifying critical knowledge gaps, this perspective aims to guide researchers toward dedicated experimental and computational studies that will deepen the understanding of spin-induced OER enhancement and accelerate the development of next-generation catalysts.
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Oct 2025
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I06-Nanoscience (XPEEM)
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Vincent
Polewczyk
,
Alexander Yu
Petrovic
,
Brice
Sarpi
,
Dirk
Backes
,
Hebatalla
Elnaggar
,
Payal
Wadhwa
,
Alessio
Filippetti
,
Giorgio
Rossi
,
Piero
Torelli
,
Giovanni
Vinai
,
Francesco
Maccherozzi
,
Bruce A.
Davidson
Diamond Proposal Number(s):
[11678]
Open Access
Abstract: In the growing field of spintronic devices incorporating antiferromagnetic materials, control of the domain configuration and Néel axis orientation is critical for technological implementations. Here we show by X-ray magnetic linear dichroism in photoelectron emission microscopy how antiferromagnetic properties of LaFeO3 (LFO) thin films can be tailored through epitaxial strain. LFO films were grown via molecular beam epitaxy with precise stoichiometric control, using substrates that span a range of strain states—from compressive to tensile—and crystal symmetries, including different crystallographic orientations. First, we show that epitaxial strain dictates the Néel axis orientation, shifting it from completely in-plane under compressive strain to completely out-of-plane under tensile strain, regardless of the substrate crystal symmetry. Second, we find that LFO films grown on cubic substrates exhibit a fourfold distribution of antiferromagnetic domains, but can be controlled by varying the substrate miscut, while those on orthorhombic substrates, regardless of strain state, form large-scale monodomains, a highly desirable feature for spintronic applications.
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Jul 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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F.
Bassato
,
S.
Mauri
,
L.
Braglia
,
A. Yu.
Petrov
,
E.
Dobovičnik
,
F.
Tavani
,
A.
Tofoni
,
P.
Ferrer
,
D.
Grinter
,
G.
Held
,
P.
D'Angelo
,
P.
Torelli
Diamond Proposal Number(s):
[33111]
Abstract: A-site doped SrTiO3 is considered as a promising substitute for traditional anodic metals in solid oxide fuel cells (SOFCs). In this study, we present the reactivity of La0.2Sr0.25Ca0.45TiO3 (LCSTO), La0.2Sr0.7TiO3 (LSTO), and SrTiO3 (STO) toward H2 by operando ambient pressure NEXAFS spectroscopy and theoretical spectra simulation with FDMNES code. The samples were synthesized by MBE (molecular beam epitaxy), hydrothermal, and modified-Pechini routes. We found that the reducibility of the samples depends not only on their stoichiometry but also on the morphology, which is determined by the synthetic method. The results of these experiments give insight into the reducibility of Ti4+ in perovskites as well as the opportunity to further optimize the synthesis of these materials to obtain the best performance for SOFC applications.
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Aug 2024
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I06-Nanoscience (XPEEM)
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Federico
Motti
,
G.
Vinai
,
Valentina
Bonanni
,
Vincent
Polewczyk
,
Paola
Mantegazza
,
Thomas
Forrest
,
Francesco
Maccherozzi
,
Stefania
Benedetti
,
Christian
Rinaldi
,
Matteo
Cantoni
,
Damiano
Cassese
,
Stefano
Prato
,
Sarnjeet S.
Dhesi
,
Giorgio
Rossi
,
Giancarlo
Panaccione
,
Piero
Torelli
Diamond Proposal Number(s):
[18810]
Abstract: A ferromagnetic (FM) thin film deposited on a substrate of
Pb
(
Mg
1
/
3
Nb
2
/
3
)
O
3
−
PbTiO
3
(PMN-PT) is an appealing heterostructure for the electrical control of magnetism, which would enable nonvolatile memories with ultralow-power consumption. Reversible and electrically controlled morphological changes at the surface of PMN-PT suggest that the magnetoelectric effects are more complex than the commonly used “strain-mediated” description. Here we show that changes in substrate morphology intervene in magnetoelectric coupling as a key parameter interplaying with strain. Magnetic-sensitive microscopy techniques are used to study magnetoelectric coupling in Fe/PMN-PT at different length scales, and compare different substrate cuts. The observed rotation of the magnetic anisotropy is connected to the changes in morphology, and mapped in the crack pattern at the mesoscopic scale. Ferroelectric polarization switching induces a magnetic field-free rotation of the magnetic domains at micrometer scale, with a wide distribution of rotation angles. Our results show that the relationship between the rotation of the magnetic easy axis and the rotation of the in-plane component of the electric polarization is not straightforward, as well as the relationship between ferroelectric domains and crack pattern. The understanding and control of this phenomenon is crucial to develop functional devices based on FM/PMN-PT heterostructures.
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Nov 2020
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I09-Surface and Interface Structural Analysis
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G.
Vinai
,
C.
Bigi
,
A.
Rajan
,
M. D.
Watson
,
T.-L.
Lee
,
F.
Mazzola
,
S.
Modesti
,
S.
Barua
,
M.
Ciomaga Hatnean
,
G.
Balakrishnan
,
P. D. C.
King
,
P.
Torelli
,
G.
Rossi
,
G.
Panaccione
Diamond Proposal Number(s):
[21429]
Abstract: Among transition-metal dichalcogenides, mono and few-layers thick
VSe
2
has gained much recent attention following claims of intrinsic room-temperature ferromagnetism in this system, which have nonetheless proved controversial. Here, we address the magnetic and chemical properties of
Fe
/
VSe
2
heterostructure by combining element sensitive x-ray absorption spectroscopy and photoemission spectroscopy. Our x-ray magnetic circular dichroism results confirm recent findings that both native mono/few-layer and bulk
VSe
2
do not show intrinsic ferromagnetic ordering. Nonetheless, we find that ferromagnetism can be induced, even at room temperature, after coupling with a Fe thin film layer, with antiparallel alignment of the moment on the V with respect to Fe. We further consider the chemical reactivity at the
Fe
/
VSe
2
interface and its relation with interfacial magnetic coupling.
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Jan 2020
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Abstract: Magnetism in monolayer (ML) VSe2 has attracted broad interest in spintronics, while existing reports have not reached consensus. Using element-specific X-ray magnetic circular dichroism, a magnetic transition in ML VSe2 has been demonstrated at the contamination-free interface between Co and VSe2. Through interfacial hybridization with a Co atomic overlayer, a magnetic moment of about 0.4 μB per V atom in ML VSe2 is revealed, approaching values predicted by previous theoretical calculations. Promotion of the ferromagnetism in ML VSe2 is accompanied by its antiferromagnetic coupling to Co and a reduction in the spin moment of Co. In comparison to the absence of this interface-induced ferromagnetism at the Fe/ML MoSe2 interface, these findings at the Co/ML VSe2 interface provide clear proof that the ML VSe2, initially with magnetic disorder, is on the verge of magnetic transition.
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Jul 2019
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I09-Surface and Interface Structural Analysis
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Anna
Regoutz
,
Isha
Gupta
,
Alexantrou
Serb
,
Ali
Khiat
,
Francesco
Borgatti
,
Tien-Lin
Lee
,
Christoph
Schlueter
,
Piero
Torelli
,
Benoit
Gobaut
,
Mark
Light
,
Daniela
Carta
,
Stuart
Pearce
,
Giancarlo
Panaccione
,
Themistoklis
Prodromakis
Diamond Proposal Number(s):
[0240]
Open Access
Abstract: TiO2 is commonly used as the active switching layer in resistive random access memory. The electrical characteristics of these devices are directly related to the fundamental conditions inside the TiO2 layer and at the interfaces between it and the surrounding electrodes. However, it is complex to disentangle the effects of film “bulk” properties and interface phenomena. The present work uses hard X-ray photoemission spectroscopy (HAXPES) at different excitation energies to distinguish between these regimes. Changes are found to affect the entire thin film, but the most dramatic effects are confined to an interface. These changes are connected to oxygen ions moving and redistributing within the film. Based on the HAXPES results, post-deposition annealing of the TiO2 thin film was investigated as an optimisation pathway in order to reach an ideal compromise between device resistivity and lifetime. The structural and chemical changes upon annealing are investigated using X-ray absorption spectroscopy and are further supported by a range of bulk and surface sensitive characterisation methods. In summary, it is shown that the management of oxygen content and interface quality is intrinsically important to device behavior and that careful annealing procedures are a powerful device optimisation technique.
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Jan 2016
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Ivana
Vobornik
,
Giancarlo
Panaccione
,
Jun
Fujii
,
Zhi-Huai
Zhu
,
Francesco
Offi
,
Benjamin R.
Salles
,
Francesco
Borgatti
,
Piero
Torelli
,
Jean Pascal
Rueff
,
Denis
Ceolin
,
Alberto
Artioli
,
Manju
Unnikrishnan
,
Giorgio
Levy
,
Massimiliano
Marangolo
,
Mamhoud
Eddrief
,
Damjan
Krizmancic
,
Huiwen
Ji
,
Andrea
Damascelli
,
Gerrit
Van Der Laan
,
Russell George
Egdell
Abstract: The influence of magnetic dopants on the electronic and chemical environments in topological insulators (TIs) is a key factor when considering possible spintronic applications based on topological surface state properties. Here we provide spectroscopic evidence for the presence of distinct chemical and electronic behavior for surface and bulk magnetic doping of Bi2Te3. The inclusion of Mn in the bulk of Bi2Te3 induces a genuine dilute ferromagnetic state, with reduction of the bulk band gap as the Mn content is increased. Deposition of Fe on the Bi2Te3 surface, on the other hand, favors the formation of iron telluride already at coverages as low as 0.07 monolayer, as a consequence of the reactivity of the Te-rich surface. Our results identify the factors that need to be controlled in the realization of magnetic nanosystems and interfaces based on TIs.
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Jun 2014
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J.
Fujii
,
B. R.
Salles
,
M.
Sperl
,
S.
Ueda
,
M.
Kobata
,
K.
Kobayashi
,
Y.
Yamashita
,
P.
Torelli
,
M.
Utz
,
C. S.
Fadley
,
A. X.
Gray
,
J.
Braun
,
H.
Ebert
,
I.
Di Marco
,
O.
Eriksson
,
P.
Thunström
,
G. H.
Fecher
,
H.
Stryhanyuk
,
E.
Ikenaga
,
G.
Van Der Laan
,
G.
Panaccione
,
J.
Minar
,
C. H.
Back
Abstract: We report high-resolution hard x-ray photoemission spectroscopy results on (Ga,Mn)As films as a function of Mn doping. Supported by theoretical calculations we identify, for both low (1%) and high (13%) Mn doping values, the electronic character of the states near the top of the valence band. Magnetization and temperature-dependent core-level photoemission spectra reveal how the delocalized character of the Mn states enables the bulk ferromagnetic properties of (Ga,Mn)As.
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Aug 2013
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