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@article{WOS:001601237600001,
title = {Observation of Topological Chirality Switching Induced Freezing of a
Skyrmion Crystal},
author = {John Fullerton and Yue Li and Harshvardhan Solanki and Sergey Grebenchuk and Magdalena Grzeszczyk and Zhaolong Chen and Makars Siskins and Kostya S Novoselov and Maciej Koperski and Elton J G Santos and Charudatta Phatak},
doi = {10.1002/adma.202513067},
times_cited = {0},
issn = {0935-9648},
year = {2025},
date = {2025-10-01},
journal = {ADVANCED MATERIALS},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {Magnetic skyrmions are topologically protected quasi-particles with a
well-defined chirality. Control over their chirality is proposed as an
additional feature for encoding data bits or as qubits in quantum
computing due to their high efficiency and stability against achiral
magnetic textures. Here it is shown that an in-plane magnetic field can
be utilized to reshape the energy barriers between different skyrmionic
bubbles (e.g., Bloch type, type-II) enabling spontaneous chirality
fluctuations with a frequency that increases with the strength of the
in-plane field. The insulating van der Waals ferromagnet CrBr3 is used
as an archetypal system for low damping, reduced energy dissipation and
a high number of magnetic phases to capture the chirality dynamics in
real time through cryo-Lorentz transmission electron microscopy. It is
observed that the interplay between the intrinsic Dzyaloshinskii-Moriya
interaction and out-of-plane field biased the chirality dynamics,
favoring one handedness over the other. A remarkable consequence of the
spontaneous chirality switching mechanism is that it induces a freezing
(or crystallization) process in the skyrmion lattice. As the bubbles
fluctuate between Bloch and type-II they elongate and shrink parallel to
the in-plane field. Subsequently, the overall lattice crystallizes along
the in-plane field direction, inducing a phase transition from a
disordered liquid state to a hexatic phase where skyrmions are highly
ordered resembling that of a solid. The results indicate chirality as an
active element in the creation of topologically protected skyrmion
crystals unveiling pathways toward chiral spintronic device platforms
with tunable embedded configuration.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001464532700001,
title = {Correlations in Magnetic Sub-Domains as an Unconventional Phase Diagram
for van der Waals Ferromagnets},
author = {Sergey Y Grebenchuk and Magdalena Grzeszczyk and Zhaolong Chen and Makars Siskins and Vladislav Borisov and Manuel Pereiro and Mikhail I Katsnelson and Olle Eriksson and Kostya S Novoselov and Maciej Koperski},
doi = {10.1002/advs.202500562},
times_cited = {2},
year = {2025},
date = {2025-07-01},
journal = {ADVANCED SCIENCE},
volume = {12},
number = {26},
publisher = {WILEY},
address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA},
abstract = {Traditional magnetic phase diagram represents a transition between the
ferromagnetic and paramagnetic states of a material under the influence
of varied temperature, magnetic field, and pressure. So far, the
ferromagnetic phase has been considered predominantly as a single type
of magnetization texture extending macroscopically in the bulk of a
crystal, existing as a ground state determined by the interactions
between localized magnetic moments arranged in a lattice. Here, it is
demonstrated that an unconventional magnetic order composed of
vertically correlated planar magnetic sub-domains occurs intrinsically
in mechanically exfoliated layers of van der Waals ferromagnet CrBr3.
Based on the visualization of the magnetic textures through magnetic
force microscopy in conjunction with the ab initio calculations of the
crystal structure in the magnetic phase and micromagnetic simulations,
the origin of the magnetic sub-domains is attributed to stacking faults
isolating a van der Waals ferromagnetic well from the bulk film due to
modifications in the interlayer exchange coupling. This enables to
create a phase diagram describing the magnetic states unique to van der
Waals ferromagnets in terms of the degree of correlation between the
magnetic sub-domains, dependent on the exchange coupling constants and
tuneable by magnetic field and temperature.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001511202800006,
title = {Thermoelastic damping across the phase transition in van der Waals
magnets},
author = {Alvaro Bermejillo-Seco and Xiang Zhang and Maurits J A Houmes and Makars Siskins and Herre S J van der Zant and Peter G Steeneken and Yaroslav M Blanter},
doi = {10.1103/PhysRevB.111.245409},
times_cited = {1},
issn = {2469-9950},
year = {2025},
date = {2025-06-01},
journal = {PHYSICAL REVIEW B},
volume = {111},
number = {24},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {A quantitative understanding of the microscopic mechanisms responsible
for damping in van der Waals nanomechanical resonators remains elusive.
In this work, we investigate van der Waals magnets, where the thermal
expansion coefficient exhibits an anomaly at the magnetic phase
transition due to magnetoelastic coupling. Thermal expansion mediates
the coupling between mechanical strain and heat flow and determines the
strength of thermoelastic damping (TED). Consequently, variations in the
thermal expansion coefficient are reflected directly in TED, motivating
our focus on this mechanism. We extend existing TED models to
incorporate anisotropic thermal conduction, a critical property of van
der Waals materials. By combining the thermodynamic properties of the
resonator material with the anisotropic TED model, we examine
dissipation as a function of temperature. Our findings reveal a
pronounced impact of the phase transition on dissipation, along with
transitions between distinct dissipation regimes controlled by geometry
and the relative contributions of in-plane and out-of-plane thermal
conductivity. These regimes are characterized by the resonant interplay
between strain and in-plane or through-plane heat propagation. To
validate our theory, we compare it to experimental data of the
temperature-dependent mechanical resonances of FePS3 resonators.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001443899000027,
title = {Nonlinear dynamics and magneto-elasticity of nanodrums near the phase
transition},
author = {Makars Siskins and Ata Keskekler and Maurits J A Houmes and Samuel Manas-Valero and Maciej Koperski and Eugenio Coronado and Yaroslav M Blanter and Herre S J van der Zant and Peter G Steeneken and Farbod Alijani},
doi = {10.1038/s41467-025-57317-4},
times_cited = {4},
year = {2025},
date = {2025-03-01},
journal = {NATURE COMMUNICATIONS},
volume = {16},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Nanomechanical resonances of two-dimensional (2D) materials are
sensitive probes for condensedmatter physics, offering new insights into
magnetic and electronic phase transitions. Despite extensive research,
the influence of the spin dynamics near a phase transition on the
nonlinear dynamics of 2D membranes has remained largely unexplored.
Here, we investigate nonlinear magneto-mechanical coupling to
antiferromagnetic order in suspended FePS3-based heterostructure
membranes. By monitoring the motion of these membranes as a function of
temperature, we observe characteristic features in both nonlinear
stiffness and damping close to the N & eacute;el temperature TN. We
account for these experimental observations with an analytical
magnetostriction model in which these nonlinearities emerge from a
coupling between mechanical and magnetic oscillations, demonstrating
that magneto-elasticity can lead to nonlinear damping. Our findings thus
provide insights into the thermodynamics and magneto-mechanical energy
dissipation mechanisms in nanomechanical resonators due to the
material's phase change and magnetic order relaxation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001177264100001,
title = {Topological Spin Textures in an Insulating van der Waals Ferromagnet},
author = {Sergey Grebenchuk and Conor Mckeever and Magdalena Grzeszczyk and Zhaolong Chen and Makars Siskins and Arthur R C McCray and Yue Li and Amanda K Petford-Long and Charudatta M Phatak and Duan Ruihuan and Liu Zheng and Kostya S Novoselov and Elton J G Santos and Maciej Koperski},
doi = {10.1002/adma.202311949},
times_cited = {24},
issn = {0935-9648},
year = {2024},
date = {2024-06-01},
journal = {ADVANCED MATERIALS},
volume = {36},
number = {24},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {Generation and control of topological spin textures constitutes one of
the most exciting challenges of modern spintronics given their potential
applications in information storage technologies. Of particular interest
are magnetic insulators, which due to low damping, absence of Joule
heating and reduced dissipation can provide energy-efficient
spin-textures platform. Here, it is demonstrated that the interplay
between sample thickness, external magnetic fields, and optical
excitations can generate a prolific paramount of spin textures, and
their coexistence in insulating CrBr3 van der Waals (vdW) ferromagnets.
Using high-resolution magnetic force microscopy and large-scale
micromagnetic simulation methods, the existence of a large region in T-B
phase diagram is demonstrated where different stripe domains, skyrmion
crystals, and magnetic domains exist and can be intrinsically selected
or transformed to each-other via a phase-switch mechanism. Lorentz
transmission electron microscopy unveils the mixed chirality of the
magnetic textures that are of Bloch-type at given conditions but can be
further manipulated into Neel-type or hybrid-type via
thickness-engineering. The topological phase transformation between the
different magnetic objects can be further inspected by standard
photoluminescence optical probes resolved by circular polarization
indicative of an existence of exciton-skyrmion coupling mechanism. The
findings identify vdW magnetic insulators as a promising framework of
materials for the manipulation and generation of highly ordered skyrmion
lattices relevant for device integration at the atomic level.
The formation of a skyrmion lattice in van der Waals ferromagnet CrBr3
opens pathways for exploration of topological spin textures in 2D
insulating crystals. These skyrmions manifest in unusual crystalline
environment characterized by centrosymmetric crystal structure and are
stabilized through dipolar rather than Dzyaloshinskii-Moriya
interactions. The construction of B-T phase diagram enables versatile
phase-switching mechanisms for controlling magnetization textures. image},
keywords = {},
pubstate = {published},
tppubtype = {article}
}