Magnetic Domain Configuration Research Articles

Femtosecond Laser-Induced Transient Magnetization Enhancement and Ultrafast Demagnetization Mediated by Domain Wall Origami.

Femtosecond laser-induced ultrafast magnetization dynamics are all-optically probed for different remanent magnetic domain states of a [Co/Pt]22 multilayer sample, thus revealing the tunability of the direct transport of spin angular momentum across domain walls. A variety of different magnetic domain configurations (domain wall origami) at remanence achieved by applying different magnetic field histories are investigated by time-resolved magneto-optical Kerr effect magnetometry to probe the ultrafast magnetization dynamics. Depending on the underlying domain landscape, the spin-transport-driven magnetization dynamics show a transition from typical ultrafast demagnetization to being fully dominated by an anomalous transient magnetization enhancement (TME) via a state in which both TME and demagnetization coexist in the system. Thereby, the study reveals an extrinsic channel for the modulation of spin transport, which introduces a route for the development of magnetic spin-texture-driven ultrafast spintronic devices.

Effect of magnetic field on macroscopic hysteresis and microscopic magnetic domains for different ferromagnetic materials

The macroscopic hysteresis of ferromagnetic materials is influenced by their microscopic magnetic domains, establishing a correspondence between the two that enables a fundamental understanding of the magnetization process of ferromagnetic materials. Based on this, this study employs the phase field method to investigate the macroscopic hysteresis and microscopic magnetic domain evolution of soft, hard, and rectangular ferromagnetic materials. The hysteresis loops of the three materials present narrow, wide and rectangular characteristics respectively, which are quantitatively consistent with the experimental data. Subsequently, the influence of the magnetic field on the macroscopic hysteresis is analyzed. The results show that the hysteresis loop area increases when the magnetic field amplitude increases. Furthermore, the proportion of each type of energy under different magnetic fields is discussed, the dominant energy terms are generally consistent for the same category of ferromagnetic materials. Additionally, the corresponding magnetic domain evolution under different magnetic field is displayed, with soft magnetic materials exhibiting no vortex structures, hard ferromagnetic materials presenting a 45° vortex structure, and rectangular magnetic material showcasing a 90° vortex structure. Finally, the asymmetric characteristics of the major hysteresis loop and minor hysteresis loops are discussed. The change of the magnetic field path leads to the corresponding change of the major and minor hysteresis loops. At the same magnetic field, distinctions in magnetic domain configurations between the major and minor hysteresis loops are evident.

The magnetic states of a van der Waals ferromagnet CrGeTe3 probed by vector-field magnetic force microscopy

We present a study on the magnetic domain configuration in the van der Waals ferromagnet CrGeTe3 using a vector-field cryogenic magnetic force microscopy. Our investigation demonstrates the influence of magnetic fields strength and angle on the magnetic domain configuration, showing the coexistence of striped and spike-like magnetic domains. This study contributes to understanding the impact of uniaxial magnetic anisotropy on the domain configuration of van der Waals ferromagnets, offering insights into stabilizing different domain patterns.

Visualizing Nanoscale Interlayer Magnetic Interactions and Unconventional Low-Frequency Behaviors in Ferromagnetic Multishelled Structures.

Precise manipulation of van der Waals forces within 2D atomic layers allows for exact control over electron-phonon coupling, leading to the exceptional quantum properties. However, applying this technique to diverse structures such as 3D materials is challenging. Therefore, investigating new hierarchical structures and different interlayer forces is crucial for overcoming these limitations and discovering novel physical properties. In this work, a multishelled ferromagnetic material with controllable shell numbers is developed. By strategically regulating the magnetic interactions between these shells, the magnetic properties of each shell are fine-tuned. This approach reveals distinctive magnetic characteristics including regulated magnetic domain configurations and enhanced effective fields. The nanoscale magnetic interactions between the shells are observed and analyzed, which shed light on the modified magnetic properties of each shell, enhancing the understanding and control of ferromagnetic materials. The distinctive magnetic interaction significantly boosts electromagnetic absorption at low-frequency frequencies used by fifth-generation wireless devices, outperforming ferromagnetic materials without multilayer structures by several folds. The application of magnetic interactions in materials science reveals thrilling prospects for technological and electronic innovation.

Magnetic Domain Wall Networked Films – Configurational Switching for Tunable Magnetization Dynamics by Perforated Thin Films

AbstractSetting the magnetization and its properties in magnetic materials and films is of the utmost fundamental and technological importance for magnetic applications and devices. Magnetic permeabilities in a material are generally defined by the acting magnetic anisotropies together with an applied magnetic field. Here, deterministic switching of the effective dynamic magnetic properties is demonstrated by tunable networks of magnetic domain walls. By perforating magnetic films, a reversible switching between different magnetization states is achieved. Due to the resulting local effective dynamic fields for the changed domain configurations, different zero‐field permeability spectra are attained for the same material structure. Using local configurational magnetic resonances confined by magnetic domain walls, deterministic switchable bimodal dynamic behavior is achieved. Dynamic magnetooptical Kerr microscopy with picosecond temporal resolution proves that the varying periodic magnetic domain configurations are responsible for the dynamic magnetic bistability. In particular, the field‐free precessional magnetic response can be reproducibly switched between 1.3 and 2.3 GHz. The magnetization dynamics can be modified by small interventions in a repeatable manner beyond fixed material and structural properties. The described fundamental mechanism enables to design new energy efficient configurational microwave devices by switching between zero‐field magnetic arrangements.

Magnetic field assisted stabilization of circular double wall domain lattice in oxidized Fe3GeTe2 flakes

The family of 2D ferromagnets is in the center of research for novel spintronics applications. Among the various 2D ferromagnets, Fe3GeTe2 has drawn significant attention since it combines a high Curie temperature with a van der Waals structure, which allows easy exfoliation, and a high spin polarization/large spin–orbit coupling. The presence of interfacial DMI in 2D ferromagnets have a significant impact on the behavior of magnetic domain walls, which are fundamental in magnetic memory and logic devices. By controlling the interfacial DMI, it is possible to manipulate the motion of domain walls and the magnetic domain configuration, which is essential for the development of efficient and reliable magnetic devices. In this study, we investigate the effect of an, inversion symmetry breaking, oxidized layer on the magnetic domain structure of Fe3GeTe2 flakes due to the emergence of interfacial DMI. By combining magneto-optical Kerr effect microscopy images and micromagnetic simulations, we study the formation of a circular double wall (CDW) domain lattice in oxidized flakes under specific field cooling and magnetic field sweeping protocols. Their formation is attributed to a competition between the exchange interaction both symmetric and antisymmetric (associated to interfacial DMI), magnetocrystalline anisotropy and the external magnetic field. The CDW domains have a diameter of several microns, a magnetic structure resembling that of a skyrmionium and are arranged in regular lattice that survives thermal fluctuations close to T c. Our results suggest that these CDW domains transition to Néel type skyrmions after a magnetic field threshold. These findings could have important implications for the design and optimization of 2D ferromagnetic materials for spintronic applications.

Tunable spin texture transformation with field-free biskyrmion over a broad temperature range in rare-earth ferrimagnets

Exploring and discovering various types of skyrmions has enriched the fundamental study and the active skyrmionics aiming at using skyrmions in spintronics due to the advantages of global stability as high-density magnetic information bit. The unique capability to introduce abundant spin structures, physical phenomena, and dynamics due to the interactions of 4f and 3d electrons push the rare-earth–transition metal (RE–TM) magnets into the research frontier again. Herein, the exotic magnetic domain configurations are discovered in traditional ThMn12-type RE–TM magnets. It is clearly demonstrated that the magnetic anisotropy alteration and magnetic coupling between the respective RE and TM sublattices are responsible for the abundant magnetic domain evolution. In particular, the field-free biskyrmions at room temperature and tunable spin texture transformation are successfully obtained via manipulating the in-plane magnetic anisotropy, which has broadened the physical mechanism and application exploration of manipulating ferrimagnetic order to generate topological spin structures in strategic rare-earth magnets.

Competition between exchange and magnetostatic energies in domain pattern transfer from BaTiO3 (111) to a Ni thin film

We use spin-polarized low-energy electron microscopy to investigate domain pattern transfer in a multiferroic heterostructure consisting of a (111)-oriented ${\mathrm{BaTiO}}_{3}$ substrate and an epitaxial Ni film. After in situ thick-film deposition and annealing through the ferroelectric phase transition, interfacial strain transfer from ferroelastic domains in the substrate and inverse magnetostriction in the magnetic thick film introduce a uniaxial in-plane magnetic anisotropy that rotates by ${60}^{\ensuremath{\circ}}$ between alternating stripe regions. We show that two types of magnetic domain wall can be initialized in principle. Combining experimental results with micromagnetic simulations, we show that a competition between the exchange and magnetostatic energies in these domain walls has a strong influence on the magnetic domain configuration.

Tuning rotational magnetization for high frequency magnetoimpedance in micro-patterned triangle spiral magnetic systems

Achieving high sensitivity, resolution, and accuracy is desirable and in high demand for magnetic sensor applications. The giant magnetoimpedance (GMI) effect has drawn intensive attention owing to its ultrasensitive response to the magnetic field. Further enhancement of the GMI effect in soft magnetic conductors (wires, ribbons, or films) is essential but represents a big challenge since the experimentally reported highest GMI ratio is still much smaller than its theoretically predicted value. Inspired by the kirigami structures, we propose a new approach for improving the GMI effect by designing triangle spiral magnetic systems. We demonstrate that the GMI ratio can be easily tuned by varying the edge width of the triangle spiral magnetic ribbon. The GMI ratio is enhanced up to 250% and 100% for the Fe 92.5 C 3.5 Si 3.9 ribbon with a 60 μm wide edge when a magnetic field of 100 Oe is aligned along the altitude and edge directions, respectively. Magnetometry indicates that upon reduction of the edge width, the improvement of magnetic susceptibility at low applied fields is correlated with the strengthened shape anisotropy. Micromagnetic simulations suggest that various closure magnetic domain configurations such as stripe and zig-zag domain structures can be formed, depending on the applied magnetic field directions, as a result of the competition of anisotropy and Zeeman energies followed in the Stoner-Wohlfarth model. The simulated results fully support the experimentally observed GMI enhancement and attribute it to the formation of transverse magnetic domains at the critical dimension of the micro-patterned magnetic ribbon system. These superior properties make the triangle-spiral GMI sensor a promising candidate for advanced sensor applications. • Various branch-width triangle spiral magnetic systems have been developed and characterized, at which optimized 60 μm width showing the best GMI effect owing to the strengthened shape anisotropy. • The GMI effect is augmented up to 250% and 100% under an applied magnetic field of 100 Oe aligned along with the altitude and edge directions, respectively. • The GMI enhancement is supported by transverse domain formations approved by OOMMF micromagnetic simulation. • Wide range of magnetic domain configurations can be formed depending on the applied magnetic field directions, originating from the competition of anisotropy and Zeeman energies followed in the Stoner-Wohlfarth model.

Magnetoelastic coupling behaviour of nanocrystalline ε-Fe2O3

Preparation of a ceramic sample which preserved the nanoscale grain sizes of ∼10–30 nm has allowed elastic and anelastic properties of ε-Fe2O3 to be investigated as functions of temperature and magnetic field strength by Resonant Ultrasound Spectroscopy in the frequency range ∼0.1–1 MHz. Formal analysis of spontaneous strains, e, from previously obtained high resolution lattice parameter data confirmed that magnetic ordering below ∼500 K is accompanied by strains of up to ∼±0.002 due to coupling with the order parameter, m, according to λem2. However, this coupling does not result in elastic softening that would be expected if the order parameter relaxed in response to an induced strain on the timescale of the acoustic resonances. Stiffening or softening during heating through ∼450–480 K of the initial as prepared material, which acquired a distinct magnetisation parallel to the stress applied during Spark Plasma Sintering, is attributed to changes in magnetic domain configurations involving preferred local alignments of individual moments of monodomain crystals. The crystallographic space group, Pna21, and magnetic space group at room temperature, Pna'21', allow ε-Fe2O3 to be both piezoelectric and piezomagnetic. It is postulated that changes in the effective coefficients of these properties for bulk samples are responsible for the observed variations in acoustic resonance frequencies according to the magnetic domain structure present. No elastic or anelastic anomalies were observed at the commensurate-incommensurate transition near 110 K. Instead, acoustic resonance frequencies changed in response to an applied magnetic field, consistent with viscous motion of magnetic domain walls and the effect of poling on piezo coefficients. Ceramic samples of ε-Fe2O3 could have potentially functional piezoelectric and/or piezomagnetic properties that are tunable by choice of magnetic and thermal history.

In-situ observation of magnetic vortices and their manipulation by external fields in Tb(Co1−xFex)5 ribbons

Nontrivial spin textures including magnetic vortices, skyrmions, and merons possess intriguing properties that are suitable for the application in further spintronics devices. The stability of topological spin textures in a broad temperature span is imperative for their potential applications as information carriers. In this study, we show the in-situ observation of the magnetic domain configuration and their manipulation under temperature and in-plane magnetic field in amorphous or nanocrystalline Tb(Co1−xFex)5 (x = 0.5, 0.8, 1.0) ribbons using Lorentz transmission electron microscopy. The results demonstrate that the formation of magnetic vortices is highly dependent on the degree of amorphization of Tb(Co1−xFex)5 ribbons and intrinsic magnetic parameters, which can be controlled by the composition. The higher the Fe content, the stronger the degree of amorphous in Tb(Co1−xFex)5 ribbons. Whereby, high-density magnetic vortices develop inside domain walls in the TbFe5 ribbon. Moreover, no matter how the degree of amorphization changes, magnetic domain structures including vortices in these ribbons have good thermal stability in the temperature range of 120–300 K, while the evolution of magnetic domains under the application of magnetic field is greatly affected by the degree of amorphization. The cross-tie domain walls consisted of magnetic vortices and antivortices form as applying a proper magnetic field in TbFe5, in contrast with the unchanged magnetic domains in Tb(Co0.5Fe0.5)5. This study provides a guideline for the design of magnetic vortex materials and soft magnetic materials.

Magnetic domain configurations of pulsed laser deposited MnBi hard magnetic films

Hard magnetic MnBi films were obtained by appropriate heat treatments of pulsed laser deposited (PLD) (Bi/Mn) films. X-ray diffraction patterns indicated a slight texture of MnBi crystallites and magnetometry measurements showed a slight preferential growth of the crystallites with their c-axis perpendicular to the film plane. Magnetic force microscopy (MFM) measurements displayed the presence of magnetic domains, whose size was in the micrometer range, and which were correlated to the MnBi grains observed in the sample. The addition of extra Mn layers did not modify significantly the previous structural and magnetic results. Nevertheless, the size of the magnetic domains increased to a few microns. However, on adding extra Bi layers, upon annealing, the MnBi grains grew with their c-axes perpendicular to the film plane. A perpendicular to the film magnetic anisotropy was deduced from the hysteresis loops, where an increase in the remanence of the magnetization was measured when the magnetic field was applied perpendicular to the film plane. In these samples, by measuring the magnetic domain configuration of the samples by MFM, we observed that the size of the magnetic domains exceeded the dimensions of the grains. This change in the magnetic structure of the films was assumed to be due to the coupling of the magnetization in the neighboring grains, and it was responsible for the decrease of the coercivity in the Bi rich samples.

Strain‐Induced Interlayer Parallel‐to‐Antiparallel Magnetic Transitions of Twisted Bilayers

AbstractThe discovery of superconductivity in twisted graphene bilayers with a magic twisting angle ≈1.1° has opened up a wide range of potential twistronic device possibilities. In this work, the twisting effects in spintronic devices are explored. In particular, a material prototype integrating spintronics, straintronics, and twistronics is developed by stacking a twisted CoFe2O4 (CFO) bilayer membrane on a Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) membrane. Phase‐field simulations are performed to study the magnetic domain configurations and switching in CFO bilayers under piezostrains. An emerging interlayer parallel‐to‐antiparallel magnetic transition of the twisted CFO bilayer induced by appropriate piezostrain pulses generated from the PMN‐PT membrane is discovered. Such a strain‐induced parallel‐to‐antiparallel magnetic transition is non‐volatile and reversible, arising from the synergistic interaction among spin, strain, and twisting order parameters. The present work provides a paradigm for designing novel spinotropic devices by taking advantage of the emerging phenomena generated by twisting.

Resonant nanodiffraction x-ray imaging reveals role of magnetic domains in complex oxide spin caloritronics.

Spin electronic devices based on crystalline oxide layers with nanoscale thicknesses involve complex structural and magnetic phenomena, including magnetic domains and the coupling of the magnetism to elastic and plastic crystallographic distortion. The magnetism of buried nanoscale layers has a substantial impact on spincaloritronic devices incorporating garnets and other oxides exhibiting the spin Seebeck effect (SSE). Synchrotron hard x-ray nanobeam diffraction techniques combine structural, elemental, and magnetic sensitivity and allow the magnetic domain configuration and structural distortion to be probed in buried layers simultaneously. Resonant scattering at the Gd L2 edge of Gd3Fe5O12 layers yields magnetic contrast with both linear and circular incident x-ray polarization. Domain patterns facet to form low-energy domain wall orientations but also are coupled to elastic features linked to epitaxial growth. Nanobeam magnetic diffraction images reveal diverse magnetic microstructure within emerging SSE materials and a strong coupling of the magnetism to crystallographic distortion.

Creating, probing and confirming tetragonality in bulk FeNi alloys

Effects derived from the simultaneous application of passive, uniform saturating magnetic field and tensile stress during long-time annealing utilizing a unique and simple processing tool, the MultiDriver furnace, are reported. In particular, the evolution of the crystalline structure and the magnetic domain configuration of severely deformed and subsequently annealed equiatomic FeNi alloys were revealed by high-energy synchrotron X-Ray diffraction and Magneto-Optic Kerr Microscopy. These alloys are known to undergo a first-order magnetic phase transformation to a chemically ordered tetragonal (L10) structure in astronomical timeframes. MultiDriver-annealed specimens are found to retain a tetragonal crystallographic state and texture that is similar to that of the precursor deformed state, with a smaller unit cell volume and a larger c/a ratio relative to those of control samples that were annealed under the same conditions but without magnetic field and stress drivers. Magnetic domain images echo these observations: while as-cast FeNi alloys exhibit domain patterns consistent with the presence of a stress-modified cubic magnetocrystalline anisotropy, large areas of domains with uniaxial anisotropy are present in MultiDriver-annealed samples. While no chemical order was demonstrated in these samples, a strategy is proposed for achieving the ordered state by employing a passive magnetic gradient in the MultiDriver furnace to enhance diffusion.

Cylindrical micro and nanowires: Fabrication, properties and applications

The state of the art in cylindrical nano and micro wires is reviewed with particular emphasis on the latest research trends. We analyze some of the key properties for prospective applications including magnetic anisotropy and micromagnetic structure, spin-caloritronics, domain wall dynamics and its control by transverse magnetic field and induced anisotropy, high frequency impedance and magnetic control of the electric polarizability, shape-memory and magnetocaloric effects in Heusler alloys wires. Cylindrical nanowires present specific magnetic domain configurations as complex vortex and transverse domains while the magnetization reversal typically involves propagation of Bloch-point domain walls. Such magnetic behavior offers new perspectives for applications in advanced technologies including spintronics, logic devices and novel magnetic recording media, functionalization and bioengineering and sensor devises. In particular, rapidly solidified glass-coated amorphous nanowires and submicron wires which constitute a novel class of ultrathin soft magnetic materials are attractive for future micro and nano sensors.Amorphous and nanocrystalline microwires prepared by rapid quenching from the melt can present quite peculiar magnetic properties, like spontaneous magnetic bistability associated with single and large Barkhausen jump and magnetoimpedance effect. Magnetic properties of amorphous microwires are related to the value and sign of the magnetostriction constant since the magnetoelastic anisotropy is one of the main sources of the magnetic anisotropy. As-prepared microwires with positive magnetostriction constant show generally rectangular hysteresis loops and fast domain wall propagation. In the case of low and negative magnetostriction, the wires demonstrate inclined hysteresis loops and large magnetoimpedance. To refine the magnetic structure, the easy anisotropy can be adjusted by annealing in the presence of a magnetic field and/or mechanical stress. Thus, the magnetic bistability in negative magnetostriction wires can be induced by annealing. Minimizing the magnetoelastic anisotropy either by adjusting the chemical composition with a low magnetostriction coefficient or by heat treatment is an appropriate route for enhancing the domain wall velocity. Tailoring the magnetic anisotropy by stress-annealing is also a promising method of the optimization of the domain wall dynamics in magnetic microwires.Soft magnetic properties and tunable magnetic structure of amorphous microwires are responsible for the magnetoimpedance effect, which preserves a high sensitivity up to GHz frequencies. This opens up novel applications based on the electric polarization of a finite-length microwire depending on the wire surface impedance near the antenna resonance, including embedded wireless sensing elements, self-sensing composites and selective microwave materials.Heusler alloys demonstrate the huge variety of physical properties that can be obtained by simple change in composition. Naturally, the efforts have been made to produce Heusler-based nano and micro wires to take advantage of variety of their physical properties in a miniature form. In this review, the emphasis is made on Heusler alloy glass-coated microwires.

Surface-sensitive magnetic characterization technique for ultrathin ferromagnetic film with perpendicular magnetic anisotropy

Ultrathin ferromagnetic films display a wealth of spectacular characteristics, one of which is that two-dimensional ferromagnetism is stabilized exclusively by magnetic anisotropies. In this work, we experimentally demonstrated the realization of ultrathin yttrium iron garnet (Y3Fe5O12) films with perpendicular magnetic anisotropy by pulsed laser deposition. A labyrinthine magnetic domain configuration in Y3Fe5O12 was identified by magnetic force microscopy, qualitatively determining that the magnetic moment possesses an out-of-plane component. Magnetic moments in the Y3Fe5O12 film were investigated by using a vibrating sample magnetometer and magnetic circular dichroism spectroscopy. Due to the surface sensitivity, the characterization technique based on magnetic circular dichroism spectroscopy presents as a high-resolution magneto-optical method to determine the magnetic property quantitatively, which has an advantage over the vibrating sample magnetometer technique commonly used for bulk crystals or powders, especially when the paramagnetic background from the supporting substrate is non-negligible. Our work introduces the burgeoning material synthesis and processing technology, and miscellaneous characterization techniques into the study of conventional magnetic oxide films, providing powerful supplements to the detection and modulation of magnetism at the nanoscale.

The calculation of magnetic domain and magnetostriction in stressed grain-oriented silicon steel

A calculation model for magnetic domain configuration and magnetostriction in grain-oriented silicon steel under tension stress is proposed. The surface lancet and transverse domains in demagnetization and magnetization states are calculated as a function of grain orientation and tension stress. Magnetostriction is calculated by incorporating the critical conditions for disappearance and reappearance of the transverse domain during the magnetization process. The magnetic domain and magnetostriction vary obviously with tension stress and misorientation angle, especially in the ranges of 5–20 MPa and 1°–5°. Negative magnetostriction is quantitatively evaluated in terms of the contribution of the reappeared transverse domain. The calculation model can accurately characterize the magnetostriction of grain-oriented silicon steel under tension stress based on the normal distribution of misorientation angle.

Electric field-induced non-volatile 90° rotation of in-plane magnetic anisotropy in TbFeCo film grown on PMN-PT(0 1 1) substrate

A TbFeCo alloy film with in-plane uniaxial magnetic anisotropy was fabricated by pulsed laser deposition on a (0 1 1)-oriented Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) substrate. By applying electric field along the surface normal, the magnetic easy axis was rotated 90° from the [0 1 ] to the [1 0 0] direction by strain-mediated magnetoelectric coupling. The modulation effect was further confirmed microscopically from variation of the magnetic domain configuration. Importantly, the magnetic easy axis remains along the [1 0 0] direction after removal of the electric field. We speculate that this non-volatile modulation was triggered by an irreversible rhombohedral to orthorhombic phase transition of PMN-PT.

Plasmon-Polariton from a Helical State in a Dirac Magnet

Electromagnetic field interacting with a topologically protected one-dimensional electron helical state is shown to support a one-dimensional plasmon-polariton, which is a collective electron excitation dressed with the electromagnetic field. The electronic helical state arises at the surface of three-dimensional topological insulator in the proximity of the ferromagnet and is localized at the magnetization domain wall. This opens the possibilities to manipulate quantum optical states by altering magnetic domain configurations. An exact spectral equation for such topological plasmon-polariton is derived.