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Spatio-temporal migration of antiferromagnetic domain walls in Sr2IrO4
Authors:
Ian Robinson,
David Yang,
Ross Harder,
Dina Sheyfer,
Longlong Wu,
Jack Griffiths,
Emil Bozin,
Mark P. M. Dean,
Jialun Liu,
Hengdi Zhao,
Gang Cao,
Angel Rodriguez-Fernandez,
Jan-Etienne Pudell,
Roman Shayduk,
James Wrigley,
Alexey Zozulya,
Rustam Rysov,
Aliaksandr Leonau,
Ulrike Boesenberg,
Joerg Hallmann,
Anders Madsen
Abstract:
By laser pump-probe time-resolved coherent magnetic X-ray diffraction imaging, we have measured the migration velocity of antiferromagnetic domain walls in the Mott insulator Sr2IrO4 at 100 K. During the laser-induced demagnetization, we observe domain walls moving at 3x10^6 m/s, significantly faster than acoustic velocities. This is understood to arise from a purely electronic spin contribution t…
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By laser pump-probe time-resolved coherent magnetic X-ray diffraction imaging, we have measured the migration velocity of antiferromagnetic domain walls in the Mott insulator Sr2IrO4 at 100 K. During the laser-induced demagnetization, we observe domain walls moving at 3x10^6 m/s, significantly faster than acoustic velocities. This is understood to arise from a purely electronic spin contribution to the magnetic structure without any role for coupling to the crystal lattice.
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Submitted 7 June, 2026; v1 submitted 10 November, 2025;
originally announced November 2025.
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Probing the Linewidth of the 12.4-keV Solid-State $^{45}$Sc Isomeric Resonance
Authors:
Peifan Liu,
Miriam Gerharz,
Berit Marx-Glowna,
Willi Hippler,
Jan-Etienne Pudell,
Alexey Zozulya,
Brandon Stone,
Deming Shu,
Robert Loetzsch,
Sakshath Sadashivaiah,
Lars Bocklage,
Christina Boemer,
Shan Liu,
Vitaly Kocharyan,
Dietrich Krebs,
Tianyun Long,
Weilun Qin,
Matthias Scholz,
Kai Schlage,
Ilya Sergeev,
Hans-Christian Wille,
Ulrike Boesenberg,
Gianluca Aldo Geloni,
Jörg Hallmann,
Wonhyuk Jo
, et al. (15 additional authors not shown)
Abstract:
The $^{45}$Sc nuclear transition from the ground to the isomeric state at 12.389~keV, with a lifetime of 0.46~s, exhibits an extraordinarily narrow natural width of 1.4~feV and a quality factor $\simeq 10^{19}$ -- surpassing those of the most precise atomic clocks -- making $^{45}$Sc a compelling platform for advanced metrology and nuclear clocks. Here we investigate how closely the spectral width…
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The $^{45}$Sc nuclear transition from the ground to the isomeric state at 12.389~keV, with a lifetime of 0.46~s, exhibits an extraordinarily narrow natural width of 1.4~feV and a quality factor $\simeq 10^{19}$ -- surpassing those of the most precise atomic clocks -- making $^{45}$Sc a compelling platform for advanced metrology and nuclear clocks. Here we investigate how closely the spectral width and quality factor of the solid-state $^{45}$Sc resonance can approach these natural limits. Using the European X-ray Free-Electron Laser, we confirm the isomer's lifetime via time-delayed incoherent $K_{α,β}$ fluorescence and observe previously unreported elastic fluorescence, yielding a partial internal conversion coefficient of 390(60). The absence of a clear nuclear forward scattering signal beyond a 2-ms delay implies environmental broadening of at least $500~Γ_{0}$ under experimental conditions, placing bounds on solid-state decoherence mechanisms. These findings set new experimental benchmarks for solid-state nuclear clock development.
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Submitted 26 August, 2025; v1 submitted 24 August, 2025;
originally announced August 2025.
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Ultrafast X-ray sonography reveals the spatial heterogeneity of the laser-induced magneto-structural phase transition in FeRh
Authors:
Maximilian Mattern,
Angel Rodriguez-Fernandez,
Roman Shayduk,
Jon Ander Arregi,
Vojtěch Uhlíř,
Ulrike Boesenberg,
Jörg Hallmann,
Wonhyuk Jo,
Aliaksandr Leonau,
Rustam Rysov,
James Wrigley,
Alexey Zozulya,
Stefan Eisebitt,
Anders Madsen,
Daniel Schick,
Jan-Etienne Pudell
Abstract:
Phase transitions are governed by both intrinsic and extrinsic heterogeneities, yet capturing their spatio-temporal dynamics remains a challenge. While ultrafast techniques track phase changes on femtosecond timescales, the spatial complexity and stochastic nature of the processes often remain hidden. Here, we present an experimental approach that combines well-established ultrafast hard-X-ray dif…
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Phase transitions are governed by both intrinsic and extrinsic heterogeneities, yet capturing their spatio-temporal dynamics remains a challenge. While ultrafast techniques track phase changes on femtosecond timescales, the spatial complexity and stochastic nature of the processes often remain hidden. Here, we present an experimental approach that combines well-established ultrafast hard-X-ray diffraction with a propagating strain pulse as a universal and non-invasive probe. This ultrafast X-ray sonography can capture the spatio-temporal phase heterogeneity in great detail by resolving the phase-specific strain response. We apply this approach to the antiferromagnetic-to-ferromagnetic magneto-structural phase transition in FeRh and identify the ferromagnetic phase to nucleate at the surface as narrow columnar domains of approximately $30\,\text{nm}$ diameter. Besides reconciling the diverse experimental results in the literature on FeRh, X-ray sonography offers a versatile platform for investigating a wide range of phase transitions accompanied by structural changes.
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Submitted 22 July, 2025;
originally announced July 2025.
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Softness and Hydrodynamic Interactions Regulate Lipoprotein Transport in Crowded Yolk Environments
Authors:
Nimmi Das Anthuparambil,
Michelle Dargasz,
Sonja Timmermann,
Anita Girelli,
Sebastian Retzbach,
Johannes Möller,
Wonhyuk Jo,
Agha Mohammad Raza,
Aliaksandr Leonau,
James Wrigley,
Frederik Unger,
Maddalena Bin,
Prince Prabhu Rajaiah,
Iason Andronis,
William Chèvremont,
Jörg Hallmann,
Angel Rodriguez-Fernandez,
Jan-Etienne Pudell,
Felix Brausse,
Ulrike Boesenberg,
Mohamed Youssef,
Roman Shayduk,
Rustam Rysov,
Anders Madsen,
Felix Lehmkühler
, et al. (5 additional authors not shown)
Abstract:
Low-density lipoproteins (LDLs) serve as nutrient reservoirs in egg yolk for embryonic development and as promising drug carriers. Both roles critically depend on their mobility in densely crowded biological environments. Under these crowded conditions, diffusion is hindered by transient confinement within dynamic cages formed by neighboring particles, driven by solvent-mediated hydrodynamic inter…
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Low-density lipoproteins (LDLs) serve as nutrient reservoirs in egg yolk for embryonic development and as promising drug carriers. Both roles critically depend on their mobility in densely crowded biological environments. Under these crowded conditions, diffusion is hindered by transient confinement within dynamic cages formed by neighboring particles, driven by solvent-mediated hydrodynamic interactions and memory effects -- phenomena that have remained challenging to characterize computationally and experimentally. Here, we employ megahertz X-ray photon correlation spectroscopy to directly probe the cage dynamics of LDLs in yolk-plasma across various concentrations. We find that LDLs undergo anomalous diffusion, experiencing $\approx$ 100-fold reduction in self-diffusion at high concentrations compared to dilute solutions. This drastic slowing-down is attributed to a combination of hydrodynamic interactions, direct particle-particle interactions, and the inherent softness of LDL particles. Despite reduced dynamics, yolk-plasma remains as a liquid, yet sluggish, balancing dense packing, structural stability, and fluidity essential for controlled lipid release during embryogenesis.
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Submitted 28 May, 2025;
originally announced May 2025.
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Dynamic X-ray coherent diffraction analysis: bridging the timescales between imaging and photon correlation spectroscopy
Authors:
Gerard N. Hinsley,
Fabian Westermeister,
Bihan Wang,
Kuan Hoon Ngoi,
Shweta Singh,
Rustam Rysov,
Michael Sprung,
Cameron M. Kewish,
Grant A. van Riessen,
Ivan A. Vartanyants
Abstract:
The advent of diffraction limited sources and developments in detector technology opens up new possibilities for the study of materials in situ and operando. Coherent X-ray diffraction techniques such as coherent X-ray diffractive imaging (CXDI) and X-ray photon correlation spectroscopy (XPCS) are capable for this purpose and provide complimentary information, although due to signal-to-noise requi…
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The advent of diffraction limited sources and developments in detector technology opens up new possibilities for the study of materials in situ and operando. Coherent X-ray diffraction techniques such as coherent X-ray diffractive imaging (CXDI) and X-ray photon correlation spectroscopy (XPCS) are capable for this purpose and provide complimentary information, although due to signal-to-noise requirements, their simultaneous demonstration has been limited. Here, we demonstrate a strategy for the simultaneous use of CXDI and XPCS to study in situ the Brownian motion of colloidal gold nanoparticles of 200 nm diameter suspended in a glycerol-water mixture. We visualise the process of agglomeration, examine the spatiotemporal space accessible with the combination of techniques, and demonstrate CXDI with 22 ms temporal resolution.
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Submitted 9 August, 2024;
originally announced August 2024.
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THz-Driven Coherent Magnetization Dynamics in a Labyrinth Domain State
Authors:
M Riepp,
A Philippi-Kobs,
L Mueller,
R Froemter,
W Roseker,
R Rysov,
M Walther,
K Bagschik,
M Hennes,
D Gupta,
S Marotzke,
S Bajt,
R Pan,
T Golz,
N Stojanovic,
C Boeglin,
G Gruebel
Abstract:
Terahertz (THz) light pulses can be used for an ultrafast coherent manipulation of the magnetization. Driving the magnetization at THz frequencies is currently the fastest way of writing magnetic information in ferromagnets. Using time-resolved resonant magnetic scattering, we gain new insights to the THz-driven coherent magnetization dynamics on nanometer length scales. We observe ultrafast demag…
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Terahertz (THz) light pulses can be used for an ultrafast coherent manipulation of the magnetization. Driving the magnetization at THz frequencies is currently the fastest way of writing magnetic information in ferromagnets. Using time-resolved resonant magnetic scattering, we gain new insights to the THz-driven coherent magnetization dynamics on nanometer length scales. We observe ultrafast demagnetization and coherent magnetization oscillations that are governed by a time-dependent damping. This damping is determined by the interplay of lattice heating and magnetic anisotropy reduction revealing an upper speed limit for THz-induced magnetization switching. We show that in the presence of nanometer-sized magnetic domains, the ultrafast magnetization oscillations are associated with a correlated beating of the domain walls. The overall domain structure thereby remains largely unaffected which highlights the applicability of THz-induced switching on the nanoscale.
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Submitted 5 December, 2023;
originally announced December 2023.