arXiv subjects

Jakub Jurczyk

Publications and source records attributed to Jakub Jurczyk.

6 recordsLinked to original sources

arXiv2026

Generation of Bloch Points with Controlled Spin Texture Using Geometrical Boundary Conditions

Bloch points are three-dimensional topological singularities in magnetization that play a key role in topological transformations of spin textures, such as skyrmion creation or annihilation. While topology often enforces the existence of Bloch points in confined geometries like cylindrical nanowires, deterministic control over their position and magnetic configuration remains challenging. Here we demonstrate the generation of Bloch points with controlled spin texture by engineering geometrical boundary conditions in three-dimensional nanomagnets. By introducing a chirality interface between two three-dimensional double-helix nanowires of opposite handedness, forming a kinked, non-collinear structure, we impose competing topological constraints that uniquely define the magnetization configuration surrounding the Bloch point. A saturating magnetic field nucleates head-to-head or tail-to-tail domain configurations at the chirality interface, producing a Bloch-point domain wall with deterministic polarity, circulation and helicity. This geometrical approach enables full three-dimensional control of Bloch point domain walls allowing deterministic engineering of their spin texture and its selective coupling to current-induced Oersted fields.

cond-mat.mes-hall↗

arXiv2026

Geometric dependence of exchange bias in tilted three-dimensional CoFe/IrMn microwires

The exchange bias (EB) effect, arising from interfacial coupling between ferromagnetic (FM) and antiferromagnetic (AF) layers, induces a unidirectional magnetic anisotropy and underpins a wide range of spintronic functionalities. Extending the EB effect to three-dimensional (3D) architectures enables investigation of interfacial coupling in non-planar structures, which is a key step toward realizing spintronic functionalities beyond planar systems. Achieving this requires the fabrication of FM/AF bilayers with smooth interfaces and well-defined thicknesses on non-planar scaffolds, together with suitable characterization methods. In this work, we realize exchange-biased 3D FM/AF microwires by combining two-photon lithography with magnetron sputtering. CoFe/IrMn bilayers are deposited on microwire scaffolds with inclination angles of 0 deg, 30 deg, 45 deg relative to the substrate, and their magnetization reversal is probed using dark-field magneto-optical Kerr effect (DF-MOKE) magnetometry. We find that the EB and coercive fields vary in a characteristic way with the inclination angle, consistent with the systematic reduction in film thickness expected from inclined directional deposition. In addition, the EB magnitude is influenced by the combined effects of surface roughness of non-planar geometries and the directional growth of the bilayer, highlighting the importance of 3D scaffold surface quality for integrating magnetic multilayers. These results provide insight into the growth and magnetic behavior of sputter-deposited magnetic multilayers with functional interfaces on 3D geometries.

cond-mat.mtrl-sci↗

arXiv2026

Magnetization reversal mechanism of double-helix nanowires probed by dark-field magneto-optical Kerr effect

Double-helix (DH) nanowires provide a platform to study the influence of geometric chirality on spin chirality. Their three-dimensional (3D) helical architecture and tunable inter-strand coupling enable control of spin chirality, including the stabilization of topological 3D magnetic states such as helical domains and domain walls, topological stray fields, and extended helical vortex/skyrmion tubes. So far, the study of these and other 3D nanostructures is usually confined to a limited number of magnetic microscopy experiments in large facilities. Here, we investigate the reversal mechanism of a single DH nanowire using Dark-Field magneto-optical Kerr effect (DF-MOKE) magnetometry under external 3D magnetic fields. By analyzing the angular dependence of the DF-MOKE signal, we fit the reversal process using established models for domain-wall nucleation and propagation, finding a characteristic behavior similar to that reported for cylindrical nanowires. Micromagnetic simulations indicate that the reversal process goes through nucleation of the helical vortex tube in a curling manner while ptychographic X-ray magnetic circular dichroism data reveal that this helical vortex tube state forms through a mixed nucleation-propagation process. These observations provide a consistent microscopic picture of reversal mediated by a helical vortex tube extending along the nanowire. Our work provides a comprehensive characterization of magnetization reversal in DH nanowires and demonstrates that DF-MOKE magnetometry is effective for probing reversal mechanisms in single 3D nanostructures. This lab-based approach expands the range of accessible experiments beyond large-scale facilities, enabling extensive exploration of the rich spin states supported by 3D nano-geometries.

cond-mat.mes-hall↗

arXiv2025

Nucleation of magnetic skyrmions on curvilinear surfaces using local magnetic fields

Magnetic skyrmions stabilized by interfacial Dzyaloshinskii-Moriya interactions (DMI) are promising candidates for applications in memory, logic, and neuromorphic computing. Beyond planar films, theoretical studies predict that curvature can influence skyrmion stability by introducing effective chiral interactions. Here, we investigate skyrmion formation on self-assembled polystyrene particles coated with Pt/Co/Ta multilayers by magnetron sputtering. Vibrating sample magnetometry reveals clear differences in the magnetic reversal behavior of the curvilinear film compared to that of the planar counterpart. Using non-invasive imaging methods such as scanning transmission X-ray microscopy and high-sensitivity in-vacuum magnetic force microscopy (MFM) with low moment magnetic tipcs, we observe a maze domain pattern for the planar films while the curvilinear film reveals three-dimensional spiraling stripe states. By employing a conventional MFM operating under ambient conditions requiring a tip with a higher magnetic moment, we demonstrate that these stripe states can rupture into metastable skyrmions located at the top of the spherical particles by applying consecutive scans. Our results demonstrate that curvilinear films offer an accessible platform for stabilizing single skyrmions using local magnetic field stimuli, opening pathways to study the interplay between interfacial and curvature-induced DMIs and enabling controlled skyrmion writing on three-dimensional magnetic architectures.

cond-mat.mes-hall↗

arXiv2025

Ligand co-deposition in focused electron beam induced nanoprinting: a predictive composition model

Recent advances in nanotechnology have created the need to manufacture three-dimensional nanostructures with controlled material composition. Focused Electron Beam Induced Deposition (FEBID) is a nanoprinting technique offering highest spatial resolution combined with the ability to directly 3D-print almost any shape. It relies on local electron-induced dissociation of metal-ligand organometallic molecules adsorbed onto a substrate. So far FEBID continuum modelling involved the surface kinetics of precursor molecules during electron irradiation and succeeded in the prediction of nanoprint shape and growth rate and forms nowadays the basis of software for 3D nano-printing of nanostructures. Here, we expand the model to the surface kinetics of detached ligands. Involving their dissociation and desorption behavior allows to predict trends in the metallic composition of the nanoprinted material and to define desirable nanoprint process windows as function of electron exposure time and flux. We present the theoretical foundations of the model, validate it experimentally for chromium and silver precursors, compare calculated values with literature data for various precursors, and discuss its potential to design new experiments. This contribution enhances our understanding of FEBID dynamics and provides a versatile framework for predictive FEBID material nano-printing.

cond-mat.mes-hall↗

arXiv2024

Fractional Skyrmion Tubes in Chiral-Interfaced Three-Dimensional Magnetic Nanowires

Magnetic skyrmions are chiral spin textures with rich physics and great potential for unconventional computing. Typically, skyrmions form in bulk crystals with reduced symmetry or ultrathin film multilayers involving heavy metals. Here, we demonstrate the formation of fractional Bloch skyrmion tubes at room temperature by 3D printing ferromagnetic double-helix nanowires with two regions of opposite chirality. Using X-ray microscopy and micromagnetic simulations, we show that the coexistence of vortex and anti-parallel spin states induces the formation of fractional skyrmion tubes at zero magnetic fields, minimising the energy cost of breaking the coupling between geometric and magnetic chirality. We also demonstrate control over zero-field states, including pure vortex, or mixed skyrmion-vortex states, highlighting the magnetic reconfigurability of these 3D nanowires. This work shows how interfacing chiral geometries at the nanoscale can enable advanced forms of topological spintronics.

cond-mat.mes-hall↗