2025
|
Ghara, S.; Winkler, M.; Schmid, S. W.; Prodan, L.; Geirhos, K.; Tsurkan, V.; Ge, Wenbo; Wu, Weida; Halbritter, A.; Krohns, S.; Kézsmárki, I. Nonvolatile electric control of antiferromagnetic states on nanosecond timescales Journal Article Phys. Rev. Lett. 135, 126704 (2025). @article{ghara_nonvolatile_2025,
title = {Nonvolatile electric control of antiferromagnetic states on nanosecond timescales},
author = {S. Ghara and M. Winkler and S. W. Schmid and L. Prodan and K. Geirhos and V. Tsurkan and Wenbo Ge and Weida Wu and A. Halbritter and S. Krohns and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/yzrk-h3rz},
doi = {10.1103/yzrk-h3rz},
year = {2025},
date = {2025-09-18},
urldate = {2025-09-01},
journal = {Phys. Rev. Lett.},
volume = {135},
number = {12},
pages = {126704},
abstract = {Electrical manipulation of antiferromagnetic (AFM) states, a cornerstone of AFM spintronics, is a great challenge, requiring novel material platforms. Here we report the full control over AFM states by voltage pulses in the insulating Co3O4 spinel well below its Néel temperature. We show that the strong linear magnetoelectric effect is fully governed by the orientation of the Néel vector. As a unique feature of Co3O4, the magnetoelectric energy can easily overcome the weak magnetocrystalline anisotropy; thus, the Néel vector can be manipulated on demand, either rotated smoothly or reversed suddenly, by combined electric and magnetic fields. We achieve the nonvolatile switching within a few tens of nanoseconds between time-reversed AFM states in macroscopic volumes by voltage pulses. These observations render quasicubic antiferromagnets, like Co3O4, an ideal platform for the ultrafast (picosecond to nanosecond) manipulation of microscopic AFM domains and may pave the way for the realization of AFM spintronic devices.},
keywords = {A4, C2},
pubstate = {published},
tppubtype = {article}
}
Electrical manipulation of antiferromagnetic (AFM) states, a cornerstone of AFM spintronics, is a great challenge, requiring novel material platforms. Here we report the full control over AFM states by voltage pulses in the insulating Co3O4 spinel well below its Néel temperature. We show that the strong linear magnetoelectric effect is fully governed by the orientation of the Néel vector. As a unique feature of Co3O4, the magnetoelectric energy can easily overcome the weak magnetocrystalline anisotropy; thus, the Néel vector can be manipulated on demand, either rotated smoothly or reversed suddenly, by combined electric and magnetic fields. We achieve the nonvolatile switching within a few tens of nanoseconds between time-reversed AFM states in macroscopic volumes by voltage pulses. These observations render quasicubic antiferromagnets, like Co3O4, an ideal platform for the ultrafast (picosecond to nanosecond) manipulation of microscopic AFM domains and may pave the way for the realization of AFM spintronic devices. |  |
Prodan, L.; Evans, D. M.; Sukhanov, A. S.; Nikitin, S. E.; Tsirlin, A. A.; Puntigam, L.; Rahn, M. C.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe3Sn2 Journal Article Phys. Rev. B 111, 184442 (2025). @article{prodan_easy-cone_2025,
title = {Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe_{3}Sn_{2}},
author = {L. Prodan and D. M. Evans and A. S. Sukhanov and S. E. Nikitin and A. A. Tsirlin and L. Puntigam and M. C. Rahn and L. Chioncel and V. Tsurkan and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.184442},
doi = {10.1103/PhysRevB.111.184442},
year = {2025},
date = {2025-05-30},
urldate = {2025-05-01},
journal = {Phys. Rev. B},
volume = {111},
number = {18},
pages = {184442},
abstract = {We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants.},
keywords = {A4, B1},
pubstate = {published},
tppubtype = {article}
}
We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants. |  |
Kong, D.; Kovács, A.; Charilaou, M.; Altthaler, M.; Prodan, L.; Tsurkan, V.; Meier, D.; Han, X.; Kézsmárki, I.; Dunin-Borkowski, R. E. Strain Engineering of Magnetic Anisotropy in the Kagome Magnet Fe3Sn2 Journal Article ACS Nano 19, 8142–8151 (2025). @article{kong_strain_2025,
title = {Strain Engineering of Magnetic Anisotropy in the Kagome Magnet Fe_{3}Sn_{2}},
author = {D. Kong and A. Kovács and M. Charilaou and M. Altthaler and L. Prodan and V. Tsurkan and D. Meier and X. Han and I. Kézsmárki and R. E. Dunin-Borkowski},
url = {https://doi.org/10.1021/acsnano.4c16603},
doi = {10.1021/acsnano.4c16603},
year = {2025},
date = {2025-02-24},
urldate = {2025-03-01},
journal = {ACS Nano},
volume = {19},
number = {8},
pages = {8142–8151},
abstract = {The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches the magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing opportunities for the development of strain-controlled devices for spintronic applications.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches the magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing opportunities for the development of strain-controlled devices for spintronic applications. |  |
Zahn, M.; Müller, A. M.; Kelley, K. P.; Neumayer, S.; Kalinin, S. V.; Kézsmarki, I.; Fiebig, M.; Lottermoser, T.; Domingo, N.; Meier, D.; Schultheiß, J. Reversible long-range domain wall motion in an improper ferroelectric Journal Article Nat. Commun. 16, 1781 (2025). @article{zahn_reversible_2025,
title = {Reversible long-range domain wall motion in an improper ferroelectric},
author = {M. Zahn and A. M. Müller and K. P. Kelley and S. Neumayer and S. V. Kalinin and I. Kézsmarki and M. Fiebig and T. Lottermoser and N. Domingo and D. Meier and J. Schultheiß},
url = {https://doi.org/10.1038/s41467-025-57062-8},
doi = {10.1038/s41467-025-57062-8},
year = {2025},
date = {2025-02-19},
urldate = {2025-02-19},
journal = {Nat. Commun.},
volume = {16},
number = {1},
pages = {1781},
abstract = {Reversible ferroelectric domain wall movements beyond the 10 nm range associated with Rayleigh behavior are usually restricted to specific defect-engineered systems. Here, we demonstrate that such long-range movements naturally occur in the improper ferroelectric ErMnO3 during electric-field-cycling. We study the electric-field-driven motion of domain walls, showing that they readily return to their initial position after having traveled distances exceeding 250 nm. By applying switching spectroscopy band-excitation piezoresponse force microscopy, we track the domain wall movement with nanometric spatial precision and analyze the local switching behavior. Phase field simulations show that the reversible long-range motion is intrinsic to the hexagonal manganites, linking it to their improper ferroelectricity and topologically protected structural vortex lines, which serve as anchor point for the ferroelectric domain walls. Our results give new insight into the local dynamics of domain walls in improper ferroelectrics and demonstrate the possibility to reversibly displace domain walls over much larger distances than commonly expected for ferroelectric systems in their pristine state, ensuring predictable device behavior for applications such as tunable capacitors or sensors.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
Reversible ferroelectric domain wall movements beyond the 10 nm range associated with Rayleigh behavior are usually restricted to specific defect-engineered systems. Here, we demonstrate that such long-range movements naturally occur in the improper ferroelectric ErMnO3 during electric-field-cycling. We study the electric-field-driven motion of domain walls, showing that they readily return to their initial position after having traveled distances exceeding 250 nm. By applying switching spectroscopy band-excitation piezoresponse force microscopy, we track the domain wall movement with nanometric spatial precision and analyze the local switching behavior. Phase field simulations show that the reversible long-range motion is intrinsic to the hexagonal manganites, linking it to their improper ferroelectricity and topologically protected structural vortex lines, which serve as anchor point for the ferroelectric domain walls. Our results give new insight into the local dynamics of domain walls in improper ferroelectrics and demonstrate the possibility to reversibly displace domain walls over much larger distances than commonly expected for ferroelectric systems in their pristine state, ensuring predictable device behavior for applications such as tunable capacitors or sensors. | |
Shiotani, T.; Waki, T.; Tabata, Y.; Kézsmárki, I.; Nakamura, H. Novel family of near-room-temperature compensated itinerant pyrochlore ferrimagnets, RInCo4 (R = Dy-Tm) Unpublished (2025), arXiv:2510.04287. @unpublished{shiotani_novel_2025,
title = {Novel family of near-room-temperature compensated itinerant pyrochlore ferrimagnets, RInCo_{4} (R = Dy-Tm)},
author = {T. Shiotani and T. Waki and Y. Tabata and I. Kézsmárki and H. Nakamura},
url = {https://arxiv.org/abs/2510.04287},
doi = {10.48550/arXiv.2510.04287},
year = {2025},
date = {2025-10-05},
urldate = {2025-10-05},
abstract = {We successfully synthesized single crystals of a series of C15b Laves phase compounds, RInCo4 (R=Dy-Tm), with Co-pyrochlore and R-fcc sublattices, and systematically studied their magnetic properties via magnetometry measurements. These itinerant cubic compounds, with Curie temperatures above room temperature, show compensated ferrimagnetism featuring an antiferromagnetic coupling between the two sublattices. From this series, DyInCo4 exhibits the highest T_C (= 368 K) and a near-room-temperature compensation point T_cp (= 295 K). T_C does not change drastically with the R atom, whereas T_cp depends on the de Gennes factor of R^3+. Another magnetization anomaly is observed in all the compounds at low temperatures, which may be indicative of changes in the lattice or magnetic structure. The easy axis the ferrimagnetic moment of DyInCo4, ErInCo4, and TmInCo4 is found at T = 5 K to be along the [001], [111] and [110] directions, respectively. However, the simple easy-axis or easy-plane ferrimagnetic picture cannot be applied to HoInCo4. These observations suggest that the R sublattice determines magnetic anisotropy and compensation, while the Co sublattice plays a role in strong magnetic ordering. The high Curie temperature, together with the magnetization compensation point near room temperature, renders these itinerant pyrochlore magnets interesting for spintronic applications. },
note = {arXiv:2510.04287},
keywords = {A4},
pubstate = {published},
tppubtype = {unpublished}
}
We successfully synthesized single crystals of a series of C15b Laves phase compounds, RInCo4 (R=Dy-Tm), with Co-pyrochlore and R-fcc sublattices, and systematically studied their magnetic properties via magnetometry measurements. These itinerant cubic compounds, with Curie temperatures above room temperature, show compensated ferrimagnetism featuring an antiferromagnetic coupling between the two sublattices. From this series, DyInCo4 exhibits the highest T_C (= 368 K) and a near-room-temperature compensation point T_cp (= 295 K). T_C does not change drastically with the R atom, whereas T_cp depends on the de Gennes factor of R^3+. Another magnetization anomaly is observed in all the compounds at low temperatures, which may be indicative of changes in the lattice or magnetic structure. The easy axis the ferrimagnetic moment of DyInCo4, ErInCo4, and TmInCo4 is found at T = 5 K to be along the [001], [111] and [110] directions, respectively. However, the simple easy-axis or easy-plane ferrimagnetic picture cannot be applied to HoInCo4. These observations suggest that the R sublattice determines magnetic anisotropy and compensation, while the Co sublattice plays a role in strong magnetic ordering. The high Curie temperature, together with the magnetization compensation point near room temperature, renders these itinerant pyrochlore magnets interesting for spintronic applications. | |
2024
|
Winkler, M.; Geirhos, K.; Tyborowski, T.; Tóth, B.; Farkas, D. G.; White, J. S.; Ito, T.; Krohns, S.; Lunkenheimer, P.; Bordács, S.; Kézsmárki, I. Anisotropic magnetocapacitance of antiferromagnetic cycloids in BiFeO3 Journal Article Appl. Phys. Lett. 125, 252902 (2024). @article{winkler_anisotropic_2024,
title = {Anisotropic magnetocapacitance of antiferromagnetic cycloids in BiFeO_{3}},
author = {M. Winkler and K. Geirhos and T. Tyborowski and B. Tóth and D. G. Farkas and J. S. White and T. Ito and S. Krohns and P. Lunkenheimer and S. Bordács and I. Kézsmárki},
url = {https://doi.org/10.1063/5.0237659},
doi = {10.1063/5.0237659},
year = {2024},
date = {2024-12-01},
urldate = {2024-12-01},
journal = {Appl. Phys. Lett.},
volume = {125},
number = {25},
pages = {252902},
abstract = {Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling. | |
Langmann, J.; Eickerling, G.; Prodan, L.; Tsirlin, A. A.; Winkler, M.; Bordács, S.; Tsurkan, V.; Kézsmárki, I. Atomic-Scale Polar Helix in Inorganic Crystals Journal Article Chem. Mater. 36, 11180–11188 (2024). @article{langmann_atomic-scale_2024,
title = {Atomic-Scale Polar Helix in Inorganic Crystals},
author = {J. Langmann and G. Eickerling and L. Prodan and A. A. Tsirlin and M. Winkler and S. Bordács and V. Tsurkan and I. Kézsmárki},
url = {https://doi.org/10.1021/acs.chemmater.4c02060},
doi = {10.1021/acs.chemmater.4c02060},
year = {2024},
date = {2024-11-04},
urldate = {2024-11-01},
journal = {Chem. Mater.},
volume = {36},
number = {22},
pages = {11180–11188},
abstract = {Chiral structures, noncentrosymmetric objects with a given handedness, emerge on all scales in nature. The most well-known chiral form, the helix, has numerous materializations not only on the microscopic scale (DNA, cholesteric liquid crystals, and spin helices) but also on macroscopic and even cosmological scales. The ongoing quest for new types of chiral structures is fueled by a wide range of fascinating phenomena observed in chiral materials, such as nonreciprocal transport and optical processes, electro-optical effects, and chiral amplification and induction. Here, we report a novel route to chirality in antipolar GaTa4Se8 crystals, where the rotation of the electric polarization vector through the unit cell traces out a helix. The determination of atomic positions using X-ray diffraction combined with ab initio calculations reveals that quasi-molecular Ta4Se4 clusters distort upon a phase transition and evoke significant local electric polarization within structural layers of the unit cell. This polarization is found to rotate in 90° steps between neighboring layers, either clockwise or anticlockwise. A similar analysis performed on two archetypal chiral compounds, α-quartz and tellurium, implies that antipolar crystals with screw-axis symmetry may generally host atomic-scale polarization helices with emergent functionalities.},
keywords = {A4, B1},
pubstate = {published},
tppubtype = {article}
}
Chiral structures, noncentrosymmetric objects with a given handedness, emerge on all scales in nature. The most well-known chiral form, the helix, has numerous materializations not only on the microscopic scale (DNA, cholesteric liquid crystals, and spin helices) but also on macroscopic and even cosmological scales. The ongoing quest for new types of chiral structures is fueled by a wide range of fascinating phenomena observed in chiral materials, such as nonreciprocal transport and optical processes, electro-optical effects, and chiral amplification and induction. Here, we report a novel route to chirality in antipolar GaTa4Se8 crystals, where the rotation of the electric polarization vector through the unit cell traces out a helix. The determination of atomic positions using X-ray diffraction combined with ab initio calculations reveals that quasi-molecular Ta4Se4 clusters distort upon a phase transition and evoke significant local electric polarization within structural layers of the unit cell. This polarization is found to rotate in 90° steps between neighboring layers, either clockwise or anticlockwise. A similar analysis performed on two archetypal chiral compounds, α-quartz and tellurium, implies that antipolar crystals with screw-axis symmetry may generally host atomic-scale polarization helices with emergent functionalities. | |
2023
|
Prodan, L.; Evans, D. M.; Griffin, S. M.; Oestlin, A.; Altthaler, M.; Lysne, E.; Filippova, I. G.; Shova, S.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn Journal Article Appl. Phys. Lett. 123, 021901 (2023). @article{prodan_large_2023,
title = {Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe_{3}Sn},
author = {L. Prodan and D. M. Evans and S. M. Griffin and A. Oestlin and M. Altthaler and E. Lysne and I. G. Filippova and S. Shova and L. Chioncel and V. Tsurkan and I. Kézsmárki},
doi = {10.1063/5.0155295},
issn = {0003-6951},
year = {2023},
date = {2023-07-01},
urldate = {2023-07-01},
journal = {Appl. Phys. Lett.},
volume = {123},
number = {2},
pages = {021901},
abstract = {We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easyplane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K-1 approximate to -1.0 x 10(6) J/m(3) at 300K to -1.3 x 10(6) J/m(3) at 2K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 mu(B)=f.u. and a magnetocrystalline anisotropy energy density of -0.57meV=f.u. (-1.62 x 10(6)J/m(3)) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of similar to 3T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness. (c) 2023 Author(s).},
keywords = {A4, A5},
pubstate = {published},
tppubtype = {article}
}
We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easyplane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K-1 approximate to -1.0 x 10(6) J/m(3) at 300K to -1.3 x 10(6) J/m(3) at 2K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 mu(B)=f.u. and a magnetocrystalline anisotropy energy density of -0.57meV=f.u. (-1.62 x 10(6)J/m(3)) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of similar to 3T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness. (c) 2023 Author(s). | |
