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Field-induced condensation of $π$ to 2$π$ soliton lattices in chiral magnets
Authors:
M. Winter,
A. Pignedoli,
M. C. Rahn,
A. S. Sukhanov,
B. Achinuq,
J. R. Bollard,
M. Azhar,
K. Everschor-Sitte,
D. Pohl,
S. Schneider,
A. Tahn,
V. Ukleev,
M. Valvidares,
A. Thomas,
D. Wolf,
P. Vir,
T. Helm,
G. van der Laan,
T. Hesjedal,
J. Geck,
C. Felser,
B. Rellinghaus
Abstract:
Chiral soliton lattices (CSLs) are nontrivial spin textures that emerge from the competition between Dzyaloshinskii-Moriya interaction, anisotropy, and magnetic fields. While well established in monoaxial helimagnets, their role in materials with anisotropic, direction-dependent chirality remains poorly understood. Here, we report the direct observation of a tunable transition from $π$ to 2$π$ sol…
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Chiral soliton lattices (CSLs) are nontrivial spin textures that emerge from the competition between Dzyaloshinskii-Moriya interaction, anisotropy, and magnetic fields. While well established in monoaxial helimagnets, their role in materials with anisotropic, direction-dependent chirality remains poorly understood. Here, we report the direct observation of a tunable transition from $π$ to 2$π$ soliton lattices in the non-centrosymmetric Heusler compound Mn1.4PtSn. Using Lorentz transmission electron microscopy, resonant elastic X-ray scattering, and micromagnetic simulations, we identify a $π$-CSL as the magnetic ground state, in contrast to the expected helical phase, which evolves into a classical 2$π$-CSL under increasing out-of-plane magnetic fields. This transition is governed by a delicate interplay between uniaxial magnetocrystalline anisotropy and magnetostatic interactions, as captured by a double sine-Gordon model. Our analysis not only reveals the microscopic mechanisms stabilizing these soliton lattices but also demonstrates their general relevance to materials with D2d, S4, Cnv, or Cn symmetries. The results establish a broadly applicable framework for understanding magnetic phase diagrams in chiral systems, with implications for soliton-based spintronic devices and topological transport phenomena.
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Submitted 14 August, 2025;
originally announced August 2025.
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Spin-to-charge conversion in orthorhombic RhSi topological semimetal crystalline thin films
Authors:
Surya N. Panda,
Qun Yang,
Darius Pohl,
Hua Lv,
Iñigo Robredo,
Rebeca Ibarra,
Alexander Tahn,
Bernd Rellinghaus,
Yan Sun,
Binghai Yan,
Anastasios Markou,
Edouard Lesne,
Claudia Felser
Abstract:
The rise of non-magnetic topological semimetals, which provide a promising platform for observing and controlling various spin-orbit effects, has led to significant advancements in the field of topological spintronics. RhSi exists in two distinct polymorphs: cubic and orthorhombic crystal structures. The noncentrosymmetric B20 cubic structure has been extensively studied for hosting unconventional…
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The rise of non-magnetic topological semimetals, which provide a promising platform for observing and controlling various spin-orbit effects, has led to significant advancements in the field of topological spintronics. RhSi exists in two distinct polymorphs: cubic and orthorhombic crystal structures. The noncentrosymmetric B20 cubic structure has been extensively studied for hosting unconventional multifold fermions. In contrast, the orthorhombic structure, which crystallizes in the Pnma space group (No. 62), remains less explored and belongs to the family of topological Dirac semimetals. In this work, we investigate the structural, magnetic, and electrical properties of RhSi textured-epitaxial films grown on Si(111) substrates, which crystallize in the orthorhombic structure. We investigate the efficiency of pure spin current transport across RhSi/permalloy interfaces and the subsequent spin-to-charge current conversion via inverse spin Hall effect measurements. The xperimentally determined spin Hall conductivity in orthorhombic RhSi reaches a maximum value of 126 ($\hbar$/e)($Ω$.cm)$^{-1}$ at 10 K, which aligns reasonably well with first-principles calculations that attribute the spin Hall effect in RhSi to the spin Berry curvature mechanism. Additionally, we demonstrate the ability to achieve a sizable spin-mixing conductance (34.7 nm$^{-2}$) and an exceptionally high interfacial spin transparency of 88$%$ in this heterostructure, underlining its potential for spin-orbit torque switching applications. Overall, this study broadens the scope of topological spintronics, emphasizing the controlled interfacial spin-transport processes and subsequent spin-to-charge conversion in a previously unexplored topological Dirac semimetal RhSi/ferromagnet heterostructure.
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Submitted 23 April, 2025; v1 submitted 23 October, 2024;
originally announced October 2024.
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In-situ monitoring the magnetotransport signature of topological transitions in the chiral magnet Mn$_{1.4}$PtSn
Authors:
Andy Thomas,
Darius Pohl,
Alexander Tahn,
Heike Schlörb,
Sebastian Schneider,
Dominik Kriegner,
Sebastian Beckert,
Praveen Vir,
Moritz Winter,
Claudia Felser,
Bernd Rellinghaus
Abstract:
Emerging magnetic fields related to the presence of topologically protected spin textures such as skyrmions are expected to give rise to additional, topology-related contributions to the Hall effect. In order to doubtlessly identify this so-called topological Hall effect, it is crucial to disentangle such contributions from the anomalous Hall effect. This necessitates a direct correlation of the t…
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Emerging magnetic fields related to the presence of topologically protected spin textures such as skyrmions are expected to give rise to additional, topology-related contributions to the Hall effect. In order to doubtlessly identify this so-called topological Hall effect, it is crucial to disentangle such contributions from the anomalous Hall effect. This necessitates a direct correlation of the transversal Hall voltage with the underlying magnetic textures. We utilize a novel measurement platform that allows to acquire high-resolution Lorentz transmission electron microscopy images of magnetic textures as a function of an external magnetic field and to concurrently measure the (anomalous) Hall voltage in-situ in the microscope on one and the same specimen. We use this approach to investigate the transport signatures of the chiral soliton lattice and antiskyrmions in Mn$_{1.4}$PtSn. Notably, the observed textures allow to fully understand the measured Hall voltage without the need of any additional contributions due to a topological Hall effect, and the field-controlled formation and annihilation of anstiskyrmions are found to have no effect on the measurend Hall voltage.
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Submitted 11 October, 2024; v1 submitted 25 September, 2024;
originally announced September 2024.
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Competing anisotropies in the chiral cubic magnet Co$_8$Zn$_8$Mn$_4$ unveiled by resonant x-ray magnetic scattering
Authors:
Victor Ukleev,
Oleg I. Utesov,
Chen Luo,
Florin Radu,
Sebastian Wintz,
Markus Weigand,
Simone Finizio,
Moritz Winter,
Alexander Tahn,
Bernd Rellinghaus,
Kosuke Karube,
Yoshinori Tokura,
Yasujiro Taguchi,
Jonathan S. White
Abstract:
The cubic $β$-Mn-type alloy Co$_8$Zn$_8$Mn$_4$ is a chiral helimagnet that exhibits a peculiar temperature-dependent behavior in the spiral pitch, which decreases from 130 nm at room temperature to 70 nm below 20 K. Notably, this shortening is also accompanied by a structural transition of the metastable skyrmion texture, transforming from a hexagonal lattice to a square lattice of elongated skyrm…
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The cubic $β$-Mn-type alloy Co$_8$Zn$_8$Mn$_4$ is a chiral helimagnet that exhibits a peculiar temperature-dependent behavior in the spiral pitch, which decreases from 130 nm at room temperature to 70 nm below 20 K. Notably, this shortening is also accompanied by a structural transition of the metastable skyrmion texture, transforming from a hexagonal lattice to a square lattice of elongated skyrmions. The underlying mechanism of these transformations remain unknown, with interactions potentially involved including temperature-dependent Dzyaloshinskii-Moriya interaction, magnetocrystalline anisotropy, and exchange anisotropy. Here, x-ray resonant magnetic small-angle scattering in vectorial magnetic fields was employed to investigate the temperature dependence of the anisotropic properties of the helical phase in Co$_8$Zn$_8$Mn$_4$. Our results reveal quantitatively that the magnitude of the anisotropic exchange interaction increases by a factor of 4 on cooling from room temperature to 20 K, leading to a 5% variation in the helical pitch within the (001) plane at 20 K. While anisotropic exchange interaction contributes to the shortening of the spiral pitch, its magnitude is insufficient to explain the variation in the spiral periodicity from room to low temperatures. Finally, we demonstrate that magnetocrystalline and exchange anisotropies compete, favoring different orientations of the helical vector in the ground state.
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Submitted 25 April, 2024; v1 submitted 22 April, 2024;
originally announced April 2024.
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Top-down fabricated reconfigurable FET with two symmetric and high-current on-states
Authors:
Maik Simon,
Boshen Liang,
Dustin Fischer,
Martin Knaut,
Alexander Tahn,
Thomas Mikolajick,
Walter M. Weber
Abstract:
We demonstrate a top-down fabricated reconfigurable field effect transistor (RFET) based on a silicon nanowire that can be electrostatically programmed to p- and n-configuration. The device unites a high symmetry of transfer characteristics, high on/off current ratios in both configurations and superior current densities in comparison to other top-down fabricated RFETs. Two NiSi2/Si Schottky junct…
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We demonstrate a top-down fabricated reconfigurable field effect transistor (RFET) based on a silicon nanowire that can be electrostatically programmed to p- and n-configuration. The device unites a high symmetry of transfer characteristics, high on/off current ratios in both configurations and superior current densities in comparison to other top-down fabricated RFETs. Two NiSi2/Si Schottky junctions are formed inside the wire and gated individually. The narrow omega-gated channel is fabricated by a repeated SiO2 etch and growth sequence and a conformal TiN deposition. The gate and Schottky contact metal work functions and the oxide-induced compressive stress to the Schottky junction are adjusted to result in only factor 1.6 higher p- than n-current for in absolute terms identical gate voltages and identical drain voltages.
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Submitted 2 July, 2020;
originally announced July 2020.