Special Session CK-6
ABSTRACTS
CK-6:IL32 Artificial van der Waals Multiferroics with Electrically Reversible Spin Splitting
E.Y. TSYMBAL, University of Nebraska-Lincoln, Department of Physics and Astronomy, Lincoln, NE, USA
Van der Waals (vdW) assembly has recently become a powerful tool to create two-dimensional (2D) materials with novel properties, often distinct from those of the individual layers. Especially interesting is polar stacking of vdW layers that breaks inversion symmetry, giving rise to switchable out-of-plane polarization in systems that are not intrinsically ferroelectric. Here, we propose to apply such polar stacking to vdW antiferromagnets to create artificial 2D multiferroics exhibiting non-relativistic spin splitting (NRSS) in their electronic band structure. Based on the spin-space group symmetry approach, we identify several representative vdW antiferromagnets which exhibit different types of NRSS when stacked into a polar bilayer. We demonstrate that NRSS can have both altermagnetic and non-altermagnetic origins and elucidate symmetry requirements for NRSS to be switchable by electric polarization. Potentially, the electric polarization switching of NRSS in AFM polar bilayers may be more practical for device applications than spin-orbit torque induced switching of the AFM order parameter.
CK-6:IL33 Nonreciprocal Charge Transport in Multiferroics and Related Materials
HONG JIAN ZHAO1, L. TAO2, Y. FU1, Y. YANG3, Y. WANG1, L. BELLAICHE4, Y. MA5, 1College of Physics, Jilin University, Changchun, China; 2School of Physics, Harbin Institute of Technology, Harbin, China; 3Department of Materials Science and Engineering, Nanjing University, Nanjing, China; 4Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas, USA; 5School of Physics, Zhejiang University, Hangzhou, China
In semiconductor PN junctions, electric currents along opposite directions feel unequal resistances [1]. Such a phenomenon, known as nonreciprocal charge transport (NCT), has recently been observed in crystalline materials including noncentrosymmetric semiconductors [2] and topological materials [3]. The NCT in crystalline materials is a highly nontrivial and a general theory on NCT is highly desired. In this talk, we will show how to understand the NCT phenomenon from the symmetry point of view, and give the selection rules for screening crystalline materials with NCT [4, 5]. We shall also demonstrate that NCT can spontaneously occur or be driven by an electric field in multiferroic and related materials [4, 5].
[1] Y. Tokura, N. Nagaosa, Nat Commun 9, 3740 (2018); [2] T. Ideue, K. Hamamoto, S. Koshikawa et al., Nat. Phys. 13, 578 (2017); [3] N. Wang, D. Kaplan Z. Zhang et al., Nature 621, 487 (2023); [4] H. J. Zhao, L. Tao, Y. Fu et al., Phys. Rev. Lett. 133, 096802 (2024); [5] H. J. Zhao, Y. Fu, Y. Yang et al., Phys. Rev. Lett. 134, 046801 (2025).
CK-6:L34 Topologically Protected Skyrmion Racetrack in Spiral Multiferroics
L. MARANZANA, Quantum Materials Theory, Italian Institute of Technology, Genoa, Italy; M. MOSTOVOY, Zernike Institute for Advanced Materials, University of Groningen, Groningen, Netherlands; N. NAGAOSA, RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan
Precise positioning of topological defects is essential for racetrack memories, where their positions along a magnetic nanotrack encode information. Traditional methods achieve nanometric precision by engineering pinning landscapes that enforce discrete steps in defect motion. However, accessing each bit requires overcoming a depinning threshold, which increases power consumption. Here, we demonstrate that spiral magnets provide a natural ruler, enabling precise positioning of skyrmionic textures. A rotating magnetic field couples directly to their positions, displacing them by exactly one spiral period per full rotation of the field. Such quantized transport of skyrmionic textures, reminiscent of Thouless pumping, is topologically protected against small perturbations. Remarkably, in spiral multiferroics, an electric field can also drive the same topological pumping. The findings establish a paradigm for topologically protected transport of spin textures and position spiral multiferroics as a natural skyrmion racetrack.
CK-6:L35 Improper Ferroelectricity in Antiferroelectric
R. KAUSHIK, L. MARANZANA, S. ARTYUKHIN, Italian Institute of Technology, Genova, Italy
K3Nb3O6(BO3)2 has been recently found to exhibit to combine hytsteresis loops typical for antiferroelectrics with ferroelectric polarization. Here we use Landau theory and first principles simulations to clarify how the 6-component primary order parameter in this peculiar multiferroic induces ferroelectric polarization, and explore the resulting topological defects.
CK-6:IL36 Novel Properties and Applications of Ferroelectric Oxide Membranes
HAOYING SUN1, LU HAN1, DIANXIANG JI1, YONG ZHANG1, XIAOQING PAN2, YUEFENG NIE1, 1College of Engineering and Applied Sciences, Nanjing University, Nanjing, China; 2Department of Physics and Astronomy, University of California, Irvine, CA, USA
Freestanding oxide membranes exhibit unprecedented structural tunability and physical properties owing to their liberation from substrate constraints, enabling scalable design of ferroelectric states with novel functionalities for electronic and photonic applications. This talk will present the exploration of ferroelectric topological structures in oxide membranes for high-density memory and vortex light field modulation. Utilizing the structural flexibility of these membranes, polar topological domains—stabilized by the balance of electrostatic, elastic, and gradient energies—can be realized across scales from nanometers to micrometers. Specifically, integrating PbTiO3/SrTiO3 bilayers onto silicon enables high-density, switchable skyrmion-like nanodomains exhibiting electrically reversible resistance states, suggesting strong potential for non-volatile memory applications. Meanwhile, engineering dome-shaped BaTiO3 membranes induces a radial flexoelectric field that creates center-convergent microdomains. These micrometre-scale topologies facilitate the generation of vortex light fields through nonlinear spin–orbit interactions, enabling dynamic control via thermal and electrical stimuli. These findings highlight the versatile potential of ferroelectric oxide membranes in enabling functional topological states for next-generation electronic and photonic technologies.
[1] L. Han, et al. Nature 603, 63 (2022); [2] H.Y. Sun, et al. Nat. Nanotech. 20, 881 (2025).
CK-6:L37 (Sm0.25Ho0.25Yb0.25Lu0.25)FeO3 High Entropy Multiferroic Ceramics
XIANG MING CHEN, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
(Sm0.25Ho0.25Yb0.25Lu0.25)FeO3 high-entropy ceramics were prepared and characterized. Dense ceramics with single phase structure in space group Pbnm were obtained, in which the homogeneous distribution of the rare-earth elements was determined. The suppressed leakage current was achieved, and a high dielectric peak with strong frequency dispersion was detected. Weak ferromagnetic behavior was determined in changed from pinched hysteresis to saturated hysteresis with decreasing temperature, while the Mr increased monotonically. Moreover, a linear magnetoelectric coefficient up to 0.75 mV/cm Oe was achieved in the present high-entropy ceramics.
CK-6:IL38 Spin-orbit-coupling in Ferroelectric vdW Heterostructures
JUNLING WANG, Department of Physics, City University of Hong Kong, Kowloon Tong, Kowloon, Hong Kong SAR
Multiferroic materials, such as BiFeO3, allow for the electric-field control of magnetization because of their magnetoelectric coupling effect. They have been studied extensively for the rich underlying physics and potential applications in spintronic devices. However, research on conventional multiferroic materials have encountered serious obstacles, e.g., small coupling coefficients of Type-I multiferroics and low temperature/high conductivity of Type-II multiferroics. Recent developments on 2D ferroelectric materials open a new paradigm in the field. Their unique layered structure allows for the coexistence of switchable polarization and high conductivity, even superconductivity. In this talk, I will discuss the unique properties of 2D ferroelectric materials and the opportunities they brought in term of electric-field control of spin and magnetization.
[1] “Sub-nanosecond Polarization Switching with Anomalous Kinetics in vdW Ferroelectric WTe2“, Yinxin Bai, Zhichao Yu, Zeyu Guan, Junjiang Tian, Chuanshou Wang, Xiaodong Yao, Yihao Yang, Yunlin Lei, Jingbo Xu, Chenhao Liu, Jinlong Zhu, Yuchen Tu, Shengchun Shen, Hongjun Xiang, Xiaoguang Li*, Changsong Xu*, Junling Wang*, Nature Communications 16, 7221 (2025); [2] Chuanshou Wang, Lu You*, David Cobden, Junling Wang*, Towards two-dimensional van der Waals ferroelectrics, Nature Materials 22, 542 (2023).
CK-6:IL39 Symmetry Engineering for Artificial Flexomagnetoelectric Effect
JINXING ZHANG, School of Physics and Astronomy, Beijing Normal University, Beijing, China; and Key Lab of Multi-scale Spin Physics, MOE, China
Symmetry engineering is explicitly effective to manipulate and even create phases and orderings in strongly correlated materials. Flexural stress is universally practical to break the space-inversion or time-reversal symmetry. In this presentation, by introducing strain gradient in a centrosymmetric antiferromagnet Sr2IrO4, the space-inversion symmetry is broken accompanying a non-equivalent O ????–Ir ???? orbital hybridization along the ???? axis. Thus, an emergent polar phase and out-of-plane magnetic moment have been simultaneously observed in these asymmetric Sr2IrO4 thin films, which both are absent in its ground state. Furthermore, upon the application of a magnetic field, such polarization can be controlled by modifying the occupied ???? orbitals through spin-orbit interaction, giving rise to a flexomagnetoelectric effect. This work provides a general strategy to artificially design multiple symmetries and ferroic orderings in strongly correlated systems. Furthermore, I will share with you about our preliminary proposal and results about the Axion detection using this artificial magnetoelectric materials.
1. Xin Liu, Ting Hu, Yujun Zhang, Xueli Xu, Runyu Lei, Biao Wu, Zongwei Ma, Peng Lv, Yuelin Zhang, Shih-Wen Huang, Jialu Wu, Jing Ma, Jiawang Hong, Zhigao Sheng, Chenglong Jia*, Erjun Kan*, Ce-Wen Nan* and Jinxing Zhang*, “Flexomagnetoelectric effect in Sr2IrO4 thin films”, Physical Review Letters 133, 156505 (2024); 2. Runyu Lei, Chen-Hui Xie, Jiayi Liu, Zhong Liu, Xin Liu, Yu Gao*, Sichun Sun*, and Jinxing Zhang*, "Detecting Axion Dark Matter by Artificial Magnetoelectric Materials", Annalen der Physik, 2025 https://doi.org/10.1002/andp.202500202.
CK-6:IL40 Electric-field Control of Skyrmions in Multiferroic Heterostructures
YONGGANG ZHAO, Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing, China
Skyrmions are topologically protected particle-like spin textures and have potential applications in information storage due to their small size and high mobility. Room-temperature skyrmions in multilayers are promising candidates for the next-generation spintronic devices with high-density, low-power consumption and non-volatility. Electric-field control of skyrmions, such as the strain-mediated electric-field control, has the advantage of ultralow power dissipation. We demonstrate strain-mediated electric-field control of skyrmions, including creation, deformation and annihilation, through magnetoelectric coupling in multiferroic heterostructure [1]. We also show that individual skyrmions on nanodots can be created and deleted by local electric fields in nanostructured multiferroic heterostructures and the control is reversible, nonvolatile and magnetic field-free [2]. Moreover, we explore room-temperature creation and manipulation of individual skyrmion bags in magnetic multilayered disks [3]. Our work will stimulate more research for electric-field control of skyrmions and other spin textures.
[1] You Ba et al., Nature Communciations, 12, 322 (2021); [2] Yutong Wang et al, Phys. Rev. Lett. In revision; [3] Quan Liu et al., Nature Communciations, 16, 125 (2025).
CK-6:IL41 Thickness-Driven Symmetry Breaking and Topological Magnetoelectric States in BiFeO3
L. CARETTA, School of Engineering & Department of Physics, Brown University, Providence, Rhode Island, USA
Magnetoelectric multiferroics - materials in which electric polarization and magnetic order are intrinsically coupled - offer a platform for ultralow-power switching, nonvolatile memory, and energy-efficient transduction. Yet, both ferroelectric and magnetic orders typically degrade in the ultrathin limit, where depolarization fields and magnetic dead layers emerge. Using BiFeO3 (BFO) as a model system, we demonstrate a multiferroic phase that not only retains both order parameters at room temperature with no apparent critical thickness, but also exhibits strong signatures of emergent spin-split magnetism stabilized by epitaxial strain and short-circuit electrostatic boundary conditions. This second-order, thickness-driven phase transition gives rise to new multiferroic topological textures, where electric and magnetic symmetries become intertwined in previously unobserved ways. Additionally, at domain boundaries, we uncover a rich hierarchy of noncollinear topological magnetoelectric structures, including polar bi-merons, polar vertices coupled to magnetic cycloid disclinations, and topological cycloid-twist states, whose stability and dynamics are intimately linked to the underlying crystal symmetry.
CK-6:IL42 Terahertz Photovoltaic Effect of Multiferroics
YOUTAROU TAKAHASHI, Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo, Japan
Multiferroic materials exhibiting spin-driven ferroelectricity offer diverse functionalities through magnetoelectric coupling. Electromagnons, spin excitations with electrical activity, are one such example. Resonantly enhanced non-reciprocal optical effects have been reported for electromagnons in the terahertz region. This presentation will outline the observation of nonlinear, nonreciprocal terahertz responses of electromagnons in multifunctional materials, specifically the bulk photovoltaic effect. It has been revealed that the terahertz photon is converted into dc current through the creation of electromagnon. This novel photovoltaic effect without photo-creation of charge carriers is explained by the extended shift current mechanism where the quantum geometric nature of electronics polarization plays the essential role. The observed terahertz functionality of multiferroics potentially enables the low-noise terahertz detection and terahertz energy conversion.
CK-6:L43 Effect of Superposition of Magnetic Field and High-frequency Electric Current on Magnetic and Electrical Properties of Composite Microwires
A. CHIZHIK, A. ZHUKOV, V. ZHUKOVA, University of Basque Country, San Sebastian, Spain
Relationship between magnetic and electrical properties of glass-coated microwires under high-frequency (HF) currents reveals a complex interplay between magnetization reversal and induced circular magnetic field. When electric current in MHz–GHz range flows through the microwire, the circular magnetic field strongly influences the surface magnetization. The mechanism of this reversal depends on the current amplitude, as the HF field induces helical states governed by amplitude and frequency. Kerr effect measurements demonstrate how HF currents alter hysteresis loop shapes, where sharp magnetization jumps replace gradual rotations. Interestingly, HF current effects contrast with tensile stress: while stress enhances circular magnetization, HF currents suppress it and modify the reversal mechanism. The strong dependence of circular coercivity on HF current parameters reflects dynamics of circular domain nucleation and propagation in outer shell, where current concentrates due to skin effect. At frequencies above 1 MHz, eddy currents damp domain-wall motion, making magnetic-moment rotation dominant mechanism behind magnetoimpedance. Thus, electrical excitation at HF fundamentally reshapes magnetic behavior, coupling magnetization processes with microwire’s electrical response.
CK-6:L44 Topologically Protected Switching of Order Parameters
S. ARTYUKHIN, L. MARANZANA, M. PARODI, A. GRANERO, IIT Genova, Genova, Italy; A. PIMENOV, TU Vienna, Austria; NAOTO NAGAOSA, RIKEN CEMS, Tokyo, Japan
Conventional switching in ferroic materials relies on nucleation and propagation of domain walls, and is widely used in computing, information storage devices and beyond. A recently discovered alternative paradigm is to leverage the physics of quantum pumps, where the potential energy surface is deformed to guide the change of the state at the energy minimum [1]. Such pumping enjoys topological protection, i.e. it is robust against small enough perturbations [1], and allows to obtain quantized displacements of order parameter textures [2]. In addition, the underlying flat energy landscapes are a rich playground for control of spins by electric fields [3]. [1] L. Ponet et al., Topologically protected magnetoelectric switching in a multiferroic, Nature 607, 81 (2022); [2] L. Maranzana, M. Mostovoy, N. Nagaosa, S. Artyukhin, Spiral multiferroics as a natural skyrmion racetrack, arXiv:2502.13083; [3] M. Ryzhkov et al., Highly controllable switching pathways in GdMn2O5, Comm.Mater., in press.
CK-6:L45 Modelling E-field Control of Magnetization in a BiFeO3-ferromagnet Heterostructure
P. DIONA, Scuola Normale Superiore di Pisa, Pisa, Italy; L. MARANZANA, S. ARTYUKHIN, Quantum Materials Theory, Italian Institute of Technology, Italy
Multiferroics offer the path to memory and logic devices where the magnetic state stores information and is controlled electrically. E-field control of insulating materials such as room-temperature multiferroic BiFeO3 is realized through ferroelectric polarization that affects octahedral rotations defining the spin rotation axis. However, most insulating magnetic materials are antiferromagnets, and uniform magnetization appears only when the material is sandwitched with a ferromagnetic metal, e.g. in MESO devices [1,2]. Incorporating the recent advances in the understanding of the E-field switching in BFO [3], Here we study the influence of the device geometry and ferromagnet parameters on the E-field induced magnetization switching in a device where BFO is covered by a layer of a metallic ferromagnet.
[1] JT Heron et al., PRL 107, 217202 (2011), Ramesh Nature 2015; [2] A. Fert et al., https://arxiv.org/abs/2311.11724; [3] N. S. Fedorova, D. E. Nikonov, J. M. Mangeri, H. Li, I. A. Young, J. Íñiguez, https://arxiv.org/abs/2307.14789
CK-6:L46 Electric Coercivity in Spiral Multiferroics
A. BUZDAKOV, L. MARANZANA, M. PARODI, M. PARRINELLO, S. ARTYUKHIN, Istituto Italiano di Tecnologia, Genova, Italy
Emerging spintronic and multiferroic technologies depend on precise control of nanoscale magnetic textures, whose stability underpins next-generation devices. In spiral multiferroics, a spin spiral induces ferroelectric polarization, leading to a particularly strong coupling between spins and electric dipoles. By augmenting atomistic spin-dynamics simulations with an enhanced-sampling method, we quantitatively map the free-energy landscapes that govern the nucleation, annihilation, and transformation of spin spirals. Our simulations reveal distinct switching pathways - meron pair nucleation for large-wavevector spirals and coherent domain reversal for small-wavevector spirals - and quantify the barrier heights that determine texture lifetimes. Surprisingly, ferroelectric switching in spiral magnets goes through the creation of skyrmionic spin textures.
CK-6:IL47 Optical Detection of Antiferromagnetic Order via Linear and Bilinear Magnetoelectric Effects
TSUYOSHI KIMURA, University of Tokyo, Tokyo, Japan
The Faraday effect and the magneto-optical Kerr effect observed in ferromagnetic materials are representative nonreciprocal optical effects, that is, optical responses which are different for counter-propagating light beams. Apart from such conventional effects, unconventional nonreciprocal optical effects occur in antiferromagnetic (AFM) materials showing linear or bilinear magnetoelectric (ME) effects. Examples of such optical effects include nonreciprocal directional dichroism (NDD) and nonreciprocal rotation of reflected light (NRR) in AFM materials showing the linear ME effect, and electric field-induced NDD in AFM materials showing the bilinear ME effect. In this presentation, we show experimental demonstrations of these nonreciprocal optical effects, which can be used to detect AFM order and distinguish domain states even in fully compensated AFM materials.
This work has been done in conjunction with K. Matsumoto, K. Kobayashi, M. Moromizato, K. Arakawa, T, Hayashida, and K. Kimura.
CK-6:L49 Innovative Approaches in Printed Magnetic Field Sensors: Flexibility, Sustainability, and Performance
S. MOSCH1, C. VOIGT1, M. VINNICHENKO1, D. MAKAROV2, 1Fraunhofer IKTS, Dresden, Germany; 2Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden, Germany
The manufacturing and application of printed magnetoresistive (MR) sensors has potential to revolutionize fields of wearable electronics, automotive engineering and others. This presentation provides a comprehensive overview of the development of anisotropic magnetoresistive (AMR) and large magnetoresistive (LMR) sensors, which are manufactured using screen printing on flexible substrates such as polymer films and ceramics. These printed sensors offer improved mechanical flexibility and the ability to produce large sensor arrays cost-effectively. AMR sensors, based on nickel-iron alloys, exhibit high sensitivity in the sub-mT range, while bismuth-based LMR sensors offer exceptional performance in higher magnetic fields above 100 mT. These conducting sensors change their electrical resistance when an external magnetic field is applied. The presentation highlights the entire process flow, including rapid laser sintering for densification of the printed structures, and introduces the essential parameters for manufacturing high-quality sensors. The applications of these sensors in position determination and human-machine interaction will be addressed as well. Initial demonstrators of flexible sensors with outstanding mechanical flexibility and large sensor arrays will be presented. The use of sustainable materials such as bismuth underscores the environmental friendliness of these technologies and demonstrates their potential for future industrial applications.