I10-Beamline for Advanced Dichroism - scattering
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Diamond Proposal Number(s):
[38952]
Open Access
Abstract: High-entropy perovskite oxides offer a promising platform for tailoring magnetic functionality through compositional complexity; however, it remains unclear how targeted substitution of 4d transition metals modifies oxygen-mediated electronic structure and element-specific magnetic interactions. To address this question, we investigate the effect of Mo and Ru substitution on the electronic structure and magnetism of high-entropy perovskite oxide thin films using O K-edge and transition-metal L-edge X-ray absorption spectroscopy, X-ray magnetic circular dichroism (XMCD), and X-ray linear dichroism. O K-edge spectra reveal that Ru enhances O 2p–metal d hybridization, whereas Mo modifies charge distribution and local exchange pathways within the transition-metal sublattice. Multiplet analysis shows that Mn and Ni retain stable Mn4+ and Ni2+ states, while Co acts as the primary charge-compensation reservoir through changes in the Co2+/Co3+ ratio. Temperature-dependent XMCD demonstrates that these substitutions selectively reshape the magnetic exchange network, redistributing spin polarization among the constituent elements. Quantitative XMCD sum-rule analysis reveals that Mo substitution produces the highest reconstructed total magnetic moment across the measured temperature range, reaching values at low temperature that are nearly an order of magnitude larger than those observed in the Ru-containing compositions. These results establish a composition-driven strategy for tuning covalency, charge redistribution, and the balance between localized and itinerant magnetism in high-entropy oxide thin films, providing a pathway toward the design of tunable spintronic and multifunctional oxide materials.
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Aug 2026
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NONE-No attached Diamond beamline
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Abstract: Antiferromagnets offer intrinsic stability against external magnetic fields, but this robustness also makes controlled manipulation of their spin structure challenging. Here we demonstrate that a thin ferromagnetic Co overlayer enables magnetic-field-induced reorientation of the Néel vector in NiO, mediated by strong interfacial coupling rather than conventional exchange bias. Using x-ray magnetic circular and linear dichroism, we show that the NiO spin structure partially aligns with the Co magnetization under applied fields, resulting in a direct correlation between ferromagnetic and antiferromagnetic domain patterns. Systematic variation of the Co thickness reveals a crossover between two distinct coupling regimes. For thin Co layers, NiO follows the Co magnetization during field cycling, whereas thicker Co layers exhibit conventional exchange bias, with NiO acting as a pinning layer. This crossover occurs at a Co thickness of approximately 3 nm, which marks the transition between inverse coupling and exchange-bias-dominated behavior.
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Apr 2026
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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]
Open Access
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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I06-Nanoscience (XPEEM)
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Lingzhi
Wen
,
Cong
Li
,
Guanshihan
Du
,
Sijie
Wu
,
Jianbing
Zhang
,
Xiaoyin
Pan
,
Clodomiro
Cafolla
,
Lizhe
Hu
,
Yongjun
Wu
,
Zijian
Hong
,
Qing
He
,
Pu
Yu
Diamond Proposal Number(s):
[42042, 36503, 34602, 26142, 22361, 38419]
Abstract: Topological polar textures have garnered significant attention for next-generation electronic devices due to associated emergent functionalities (e.g., chirality, enhanced conductivity, and negative capacitance). Most studies stabilize topological textures using depolarization field in ferroelectric- dielectric superlattices or heterostructures; however, the lack of direct electrical contacts dramatically hinders the corresponding field-driven control and applications. Here, the formation of electric-field-switchable Néel-type polar skyrmions at room temperature is demonstrated in Ba0.8Sr0.2TiO3 (BSTO) thin films directly grown on metallic SrRuO3 electrodes. In this study, strategic Sr substitution is employed to engineer the Landau energy landscape of ferroelectric material BaTiO3, which eventually facilitates the coexistence of multiple polarization states without sacrificing room-temperature ferroelectricity. Piezoelectric force microscopy (PFM) uncovers a critical BSTO thickness to host the phenomena: conventional ferroelectric domains dominate 60-nm thick BSTO, whereas high-density topological polar textures emerge in 10-nm thick BSTO. Specifically, vector-PFM analysis identifies two stable skyrmion states in 10-nm BSTO with convergent- and divergent- in-plane polarization components. Importantly, an electric-field-driven interconversion between these topological states is demonstrated by reconfiguring the free-energy landscape, which is also supported by the phase-field simulations. This work provides a direct pathway of using metallic electrodes for the dynamic control of topological ferroelectrics in functional devices.
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Nov 2025
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I10-Beamline for Advanced Dichroism - scattering
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Andrey D.
Poletayev
,
Robert J.
Green
,
Jack E. N.
Swallow
,
Lijin
An
,
Leanne
Jones
,
Grant
Harris
,
Peter
Bencok
,
Ronny
Sutarto
,
Jonathon P.
Cottom
,
Benjamin J.
Morgan
,
Robert A.
House
,
Robert S.
Weatherup
,
M. Saiful
Islam
Diamond Proposal Number(s):
[33062, 30644]
Open Access
Abstract: Nickelate materials offer diverse functionalities for energy and computing applications. Lithium nickel oxide (LiNiO2) is an archetypal layered nickelate, but the electronic structure of this correlated material is not yet fully understood. Here we investigate the temperature-dependent speciation and spin dynamics of Ni ions in LiNiO2. Ab initio simulations predict that Ni ions disproportionate into three states, which dynamically interconvert and whose populations vary with temperature. These predictions are verified using x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and resonant inelastic x-ray scattering at the Ni L3,2-edge. Charge-transfer multiplet calculations consistent with disproportionation reproduce all experimental features. Our results support a model of dynamic disproportionation that explains diverse physical observations of LiNiO2, including magnetometry, thermally activated electronic conduction, diffractometry, core-level spectroscopies, and the stability of ubiquitous antisite defects. This unified understanding of the material properties of LiNiO2 is important for applications of nickelate materials as battery cathodes, catalysts, and superconductors.
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Oct 2025
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I06-Nanoscience (XPEEM)
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Martin
Jourdan
,
Jonathan
Bläßer
,
Guzmán Orero
Gámez
,
Sonka
Reimers
,
Lukas
Odenbreit
,
Miriam
Fischer
,
Yuran R.
Niu
,
Evangelos
Golias
,
Francesco
Maccherozzi
,
Armin
Kleibert
,
Hermann
Stoll
,
Mathias
Klaui
Diamond Proposal Number(s):
[37862]
Abstract: Antiferromagnets are promising candidates for ultrafast spintronic applications, leveraging current-induced spin-orbit torques. However, experimentally distinguishing between different switching mechanisms of the staggered magnetization (Néel vector) driven by current pulses remains a challenge. In an exemplary study of the collinear antiferromagnetic compound Mn2Au, we demonstrate that slower thermomagnetoelastic effects predominantly govern switching over a wide parameter range. In the regime of short current pulses in the nanosecond range, however, we observe fully Néel spin-orbit torque driven switching. We show that this ultrafast mechanism enables the complete directional alignment of the Néel vector by current pulses in device structures.
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Sep 2025
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I06-Nanoscience (XPEEM)
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Diamond Proposal Number(s):
[12893, 5888]
Open Access
Abstract: The elastic degree of freedom is widely exploited to mediate magnetoelectric coupling between ferromagnetic films and ferroelectric substrates. For epitaxial Fe films grown on clean BaTiO3 substrates, shear strain can determine the underlying magnetoelastic coupling. Here, we use PhotoEmission Electron Microscopy of ferroic Fe and BaTiO3 domains, combined with micromagnetic simulations, to directly reveal an inverted interfacial magnetoelastic coupling in the low-dimensional limit. We show that the magnetocrystalline anisotropy competes with the epitaxial shear strain to align the local magnetization of ultrathin Fe films close to the local polarization direction of the ferroelectric BaTiO3 in-plane domains. Poling the BaTiO3 substrate creates c-domains with no shear strain contribution with the local magnetization rotated by ~45°. Tuning shear strain magnetoelastic contributions suggests new routes for designing magnetoelectric devices.
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Sep 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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I10-Beamline for Advanced Dichroism - scattering
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Hetian
Chen
,
Dingsong
Jiang
,
Yujun
Zhang
,
Xiaofu
Qiu
,
Yuhan
Liang
,
Qinghua
Zhang
,
Fangyuan
Zhu
,
Takuo
Ohkochi
,
Mingfeng
Chen
,
Yue
Wang
,
Jingchun
Liu
,
Qing
He
,
Jing
Ma
,
Pu
Yu
,
Yuanhua
Lin
,
Tianxiang
Nan
,
Di
Yi
Diamond Proposal Number(s):
[38419]
Open Access
Abstract: Pure spin current enables the transport of spin information without charge flow, providing opportunities for next-generation information technologies. A pure spin current polarizer, capable of controlling both its transmittance and spin polarization, is critical for the development of spintronics; however, it has not yet been demonstrated. Here, we demonstrate a highly efficient pure spin current polarizer at room temperature using a single-domain antiferromagnetic insulator film, through structural engineering and spin-lattice coupling. Our device exhibits a large differential magnon current transmittance at room temperature. Remarkably, we find that the spin polarization of the transmitted magnon current aligns with the Néel vector of the polarizer. This enables a large modulation of damping-like torque and generation of out-of-plane-polarized magnon current, offering alternative routes for developing energy-efficient spintronic devices. We anticipate that this pure spin current polarizer will serve as a building block for spintronics based on pure spin current.
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Jul 2025
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I06-Nanoscience (XPEEM)
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Diamond Proposal Number(s):
[35404]
Open Access
Abstract: Antiferromagnets (AFs) are characterized by spin structures that are resistant to external magnetic fields, rendering them ideal for persistent information storage but challenging to control. This study demonstrates that a thin ferromagnetic adlayer can serve as a magnetic ‘lever’ to provide a strong handle on the spin texture of an adjacent antiferromagnet. In bilayers composed of NiO(001) and Co, the expected exchange bias effect—a unidirectional shift in the Co hysteresis due to coupling with NiO—is notably absent. Instead, a strong interfacial coupling is observed, causing the NiO to partially follow the magnetization of Co under an applied magnetic field. Using x-ray magnetic linear dichroism, we detect an inversion of dichroism, indicating a reorientation of the Néel vector in NiO. X-ray spectromicroscopy imaging further reveals a direct correlation between ferromagnetic and antiferromagnetic domain structures. These findings are explained using a toy model that distinguishes between stable and unstable AF domains, highlighting the dynamic interplay between NiO and the Co adlayer in the presence of a magnetic field.
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Jan 2025
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