Magnetic Layer Research Articles

Insulating and flexible electromagnetic-shielding nanofiber composite film for direct wrapping on electronics even in harsh conditions

Current electromagnetic interference (EMI) shielding materials mainly depends on electrical conductivity, it still remains great challenges to avoid short-circuit risks and assemble into macroscopic films with strong mechanical strength. To address these problems, we rationally design and prepare a multilayer-structured EMI shielding nanocomposite film (P-Co-MX), where MOF-derived porous Co–C as the magnetic layer and MXene as the conductive layer are sandwiched between two poly(m-phenylene isophthalamide) (PMIA) nanofiber membranes, with the PMIA membranes as insulating and protection layers. Benefiting from the rational design of multi-layer structure, P-Co-MX exhibits high EMI shielding effectiveness in X-band (8.2–12.4 GHz) with absorption-dominated EMI shielding feature. Owing to the protection of PMIA nanofiber layers, P-Co-MX shows high resistivity, excellent flexibility and stable EMI shielding performance even in harsh conditions, including 200 ℃ high temperature, − 196 ℃ ultralow-temperature and corrosive conditions (pH = 3). These unique features allow for direct wrapping on the signal lines in highly miniaturized and flexible electronics to solve EMI issue.Graphical

Signatures of the quantum spin liquid state in triangular-based zig-zag polyaromatic hydrocarbon radicals.

Alkali-metal doped polyaromatic hydrocarbons (PAHs) have shown great potential in realizing exotic states of matter such as quantum spin liquids (QSLs). However, it is challenging to obtain new pure-phase candidates and perform experimental identifications accordingly. Here, we report the discovery and characterization of Cs(chrysene˙-)(THF)0.5·(THF)0.25 (1, THF = tetrahydrofuran), a pure-phase spin-½ organic magnet composed of triangular-based zig-zag magnetic layers, which give rise to strong spin frustration. Electron paramagnetic resonance and optical analyses show 1 is a Mott insulator. Despite the strong antiferromagnetic coupling, low-temperature specific heat and ac susceptibility demonstrate the absence of both long-range magnetic order and spin-glass phases down to 55 mK. Magnetic specific heat can be fitted to the power law, implying gapless spin excitation. Muon spin relaxation reveals constant spin fluctuation rates, suggesting persistent slow dynamics down to 0.3 K. Our results highlight PAHs as a promising avenue for exploring new QSLs.

Computational study of skyrmion stability and transport on W/CoFeB

Skyrmions are topologically protected magnetic structures originating from Dzyaloshinbskii–Moriya Interaction (DMI) which can be driven by a spin-polarized current making it a candidate for many different novel spintronic devices. However, the transport velocity is proportional to the size of the skyrmion rendering the effort of miniaturizing spintronics devices useless indicating that it is not possible to realise high-speed transport, small size and low operating current at the same time. One approach to solving the trilemma is to increase the spin Hall angle , the conversion ratio between charge current and spin current, in the heavy metal layer. For example, beta-tungsten (-W) has attracted attention due to its high spin Hall angle, abundance in nature and the potential to combine with other materials to form complex structures. To characterise the use of -W as a heavy metal layer along with a CoFeB magnetic layer, the interfacial DMI and the external field required to generate skyrmions were estimated to be 1.5 and 0.1 T respectively, which were confirmed to be realistic. In that case, the about 10 nm diameter skyrmion was transported under SOT at a velocity of about 40 m/s, which has the potential for skyrmion-based unconventional computing devices like skyrmion race track memory and logic gate.

Impact of GdOx insertion on magnetic anisotropy and damping in double-barrier magnetic stacks

For the realization of high-performance spintronic devices, the development of novel magnetic materials/structures satisfying both large perpendicular magnetic anisotropy (PMA) and ultra-low Gilbert damping is strongly desired. Here, we show that the insertion of an ultrathin GdOx layer as a capping in double-barrier ultrathin magnetic stacks provides such a solution. The inserted GdOx capping layer prevents unintended intermixing among the magnetic layer (CoFeB) and oxide layers (MgO and MgFeO), suppressing the deterioration of both the PMA and the Gilbert damping. Remarkably, the variation in the effective oxygen doping rate of the GdOx layer strongly influences both the PMA and the Gilbert damping, likely affected by a change in the polarization of the orbital magnetic moment. As a result, the GdOx inserted stacks present considerable effective PMA values (a maximum of ∼0.55 erg/cm2) while simultaneously maintaining an ultra-low Gilbert damping (a minimum of ∼1.68 × 10−3) within the range of 1.0–1.5 nm CoFeB thicknesses. These results pave the way to realize practical spintronic devices by providing reliable magnetic structures for efficient spin manipulation.

Magneto-ionic vortices: voltage-reconfigurable swirling-spin analog-memory nanomagnets

Rapid progress in information technologies has spurred the need for innovative memory concepts, for which advanced data-processing methods and tailor-made materials are required. Here we introduce a previously unexplored nanoscale magnetic object: an analog magnetic vortex controlled by electric-field-induced ion motion, termed magneto-ionic vortex or “vortion”. This state arises from paramagnetic FeCoN through voltage gating and gradual N3– ion extraction within patterned nanodots. Unlike traditional vortex states, vortions offer comprehensive analog adjustment of key properties such as magnetization amplitude, nucleation/annihilation fields, or coercivity using voltage as an energy-efficient tuning knob. This manipulation occurs post-synthesis, obviating the need for energy-demanding methods like laser pulses or spin-torque currents. By leveraging an overlooked aspect of N3– magneto-ionics—planar ion migration within nanodots—precise control of the magnetic layer’s thickness is achieved, which enables reversible transitions among paramagnetic, single-domain, and vortion states, offering future prospects for analog computing, multi-state data storage, or brain-inspired devices.

Structure of the magnetic layer of the axial part of the mid-Atlantic ridge between the Charlie-Gibbs and the maxwell transform faults

Structure of the magnetic layer of the axial part of the mid-Atlantic ridge between the Charlie-Gibbs and the maxwell transform faults

Study on thin-layer broadband metamaterial absorber based on composite multi-opening ring pattern of magnetic dielectric layers

Balancing the thickness and bandwidth of electromagnetic wave–absorbing materials has been a challenging task. In this study, a thin and broadband metamaterial absorber consisting of a frequency selective surface (FSS) layer compounded with a magnetic dielectric layer was proposed. The changes in the wave absorbing properties of the absorbers with different numbers of openings in the open circular structure and combinations of open circular rings were analyzed. After obtaining the optimum combination of patterns, the effect of parameter variations on the microwave absorption properties of metamaterial wave absorbers was investigated. The test results show that the optimized metamaterial absorber has a thickness of 1.7 mm, a simulated absorption bandwidth of up to 10.0 GHz, and a microwave reflection loss of less than − 10 dB in the frequency band of 8.0–18.0 GHz. The absorber was prepared and its reflection loss was measured. It is found that these test results have the same trend as the simulation results, which verifies the feasibility of the metamaterial absorber structure design; the proposed two-layer magnetic dielectric composite FSS structure improves the overall impedance matching, avoids the electromagnetic wave being reflected in the surface, and makes the electromagnetic wave enter the interior more; when the resonant absorption peak generated by the introduction of FSS is close to the absorption peak generated by the magnetic dielectric layer, continuous absorption will be achieved, which is the reason for the wide absorption band of the metamaterial absorber. This novel structure takes into account the characteristics of thin layer, broadband absorption, and polarization insensitivity, which has a potential application prospect in stealth technology.

Wafer-level magnetic field biased single domain soft magnetic layers by integrated NdFeB micromagnets

Single magnetic domain soft magnetic films are the basis for many magnetic field sensing applications. The absence of magnetic domain walls reduces magnetic noise, which is relevant for magnetic sensing layers and supporting structures such as magnetic shields and flux concentrators. Here, the use of wafer-level integrated NdFeB micromagnets for on-chip field biasing of soft magnetic submicrometer thick layers for magnetic domain control is presented. Effective bias field strengths are modeled and experimentally evaluated using a magnetooptical indicator film technique. Single magnetic domain behavior in the soft magnetic layers is demonstrated. Effects of the granular micromagnet structure on the magnetic field homogeneity are discussed. The demonstrated integrated magnetic biasing scheme is applicable to various magnetic layer-based field sensing devices benefiting from single magnetic domain behavior.

High spin–orbit torque efficiency in Pt/Co/Tb/W repetition structures with broken spatial inversion symmetry

Abstract Spin-orbit torque (SOT) is an attractive phenomenon as a method of current-induced control of magnetization obtained at the interface between the heavy metal and magnetic layers. We investigated SOT dependence on the stacking structure, namely, [Pt/Co]n, [Pt/Co/Tb]n, or [Pt/Co/Tb/W]n where n is the repetition number because the repetition structure guarantees the thermal stability of magnetization. Whereas the SOT is negligibly small in the repetition structure [Pt/Co]10 because the SOT from the top and bottom Pt is canceled out, we observed finite SOT in [Pt/Co/Tb]10 induced by breaking a spatial inversion symmetry. Furthermore, the SOT of [Pt/Co/Tb/W]10 was more than three times higher than that of [Pt/Co/Tb]10 because the net spin Hall torque was enhanced by sandwiching Co with Pt and W with the opposite polarity of spin Hall angles. In addition, we clarified that the magnetization is reduced due to the intermixing at the Co/Tb interface by X-ray diffractions and composition depth profiles, that is another reason for the SOT improvement. These results are expected to provide a new foothold for the control of magnetization in various spintronic devices.

Electrical mutual switching in a noncollinear-antiferromagnetic–ferromagnetic heterostructure

Spin-orbit torque (SOT) provides a promising mechanism for electrically encoding information in magnetic states. Unlike existing schemes, where the SOT is passively determined by the material and device structures, an active manipulation of the intrinsic SOT polarity would allow for flexibly programmable SOT devices. Achieving this requires electrical control of the current-induced spin polarization of the spin source. Here we demonstrate a proof-of-concept current-programmed SOT device. Using a noncollinear-antiferromagnetic/nonmagnetic/ferromagnetic Mn3Sn/Mo/CoFeB heterostructure at zero magnetic field, we show current-induced switching in the CoFeB layer due to the spin current polarized by the magnetic structure of the Mn3Sn; by properly tuning the driving current, the spin current from the CoFeB further reverses the magnetic orientation of the Mn3Sn, which determines the polarity of the subsequent switching of the CoFeB. This scheme of mutual switching can be achieved in a spin-valve-like simple protocol because each magnetic layer serves as a reversible spin source and target magnetic electrode. It yields intriguing proof-of-concept functionalities for unconventional logic and neuromorphic computing.

Tailoring of Creep Regime Domain Wall Dynamics in Perpendicularly Magnetized Pd/Co/Pd Trilayers

AbstractUnderstanding magnetic domain wall (DW) dynamics is vital for improving the performance of heavy metal/ferromagnet based spintronic devices. Pd/Co/Pd multilayers hosting perpendicular magnetic anisotropy and interfacial Dzyaloshinskii‐Moriya interaction are prototypes for high density magnetic memory devices. This work presents the creep regime DW dynamics in Pd/Co/Pd trilayers with Ta buffer layer excited by symmetric field‐induced domain wall motion using Kerr microscopy. A systematic increment of DW velocity with increasing Co thickness is observed. SQUID‐VSM measurements reveal that the effective anisotropy constant decreases with the Co layer, leading to an increased DW width. Kerr microscopy images confirm that the DW is becoming rougher with magnetic layer thickness because of the dominance of magnetostatic energy over the DW energy. Hard X‐ray photoemission spectroscopy (HAXPES) reveals the presence of alloying at interfaces of Co/Pd. The asymmetry in magnetic circular dichroism HAXPES at the Pd 3d edge pictures the induced magnetic moment in Pd which is consistent with the larger saturation magnetization obtained from vibrating sample magnetometry. Extended X‐ray absorption fine structure performed in out‐of‐plane and in‐plane geometry shows the disordered nature of the Co local environment with the interdiffusion of Pd atoms into Co causing an asymmetry in the bonds.

An Investigation of Parameter Dimension Reduction Optimization of PMA-Synrm

The rotor of a permanent magnet-assisted synchronous reluctance (PMA-Synrm) motor mostly adopts the structure of a multi-layer magnetic barrier and multi-layer ferrite, which leads to the design parameters of this kind of motor increase with the increase in the number of magnetic barrier layers. A large number of design parameters are coupled with each other, which makes the optimization design of a permanent magnet-assisted synchronous reluctance motor particularly difficult. In this paper, a 7.5 kW, 1500 rpm permanent magnet-assisted synchronous reluctance motor is taken as the research object, and the optimization design of parameter dimension reduction is studied. The rotor structure of the motor is a combination of five layers of magnetic barrier and five layers of ferrite. By using the parameter dimension reduction method proposed in this paper, the number of parameters involved in the optimization is reduced from 26 to 7, which greatly improves the optimization efficiency of this kind of motor and realizes the comprehensive global optimization design of a permanent magnet-assisted synchronous reluctance motor. This paper provides a reference for the optimization of a permanent magnet-assisted synchronous reluctance motor.

Additive manufacturing of Fe-6.5Si cores with metal-insulator-metal structure via dual-nozzle material extrusion (MEX) technology

ABSTRACT This study proposes a novel approach for fabricating Fe-6.5 wt. %Si (Fe-6.5Si) soft magnetic cores using a dual-nozzle material extrusion (MEX) three-dimensional (3D) printing technology followed by a spark plasma sintering (SPS) process. A SiO2 insulator was printed between the Fe-6.5Si layers to fabricate metal–insulator-metal (MIM)-structured cores. Densified Fe-6.5Si soft magnetic cores (over 99%) were obtained owing to the resolution of the sintering problem with Fe-6.5Si because of its brittle nature using SPS. The magnetic core with a 0.2 mm-printed insulator (MC0.2) achieved a uniform insulator thickness of approximately 85 µm. Despite MC0.2 being approximately three times thicker than the single Fe-6.5Si layer (magnetic core single layer, MCS), a SiO2 insulator used in the cores of MC0.2 and MCS, resulted in comparable eddy current losses at 1 kHz. This highlighted the effectiveness of the MIM structure in suppressing the eddy currents. Thus, the proposed approach offers a promising solution for overcoming the geometric limitations of traditional stamping processes and paves the way for advanced magnetic core applications in additive manufacturing.

A New Interpretation for the Hot Corona in Active Galactic Nuclei

Abstract This work attempts to provide a new interpretation for the hot corona in active galactic nuclei (AGNs). A thin parabolic magnetic reconnection layer, anchored at the innermost disk and extending along the boundary of the magnetic tower for a few tens of gravitational radii, serves as a hard-X-ray source above the disk. Within this reconnection layer, the tearing instability leads to the formation of a chain of plasmoids, which contain relativistic electrons that generate X-ray radiation through inverse-Compton (IC) scattering of soft photons emitted by the accretion disk. Based on previous theoretical works and numerical simulations, we develop a heuristic framework to parameterize the geometry and magnetization of the reconnection layer, as well as to compute both the power of the IC-scattering radiation and the height of the reconnection layer. Our model allows for a quantitative investigation of the relation between the height of the corona and the X-ray radiation luminosity, which can be directly compared against the observed relation from X-ray reverberation mapping of individual AGNs. The theoretical results are in good agreement with the observations of IRAS 13224-3809, indicating the validation of our model.

Spin transport properties in a topological insulator sandwiched between two-dimensional magnetic layers

Non-trivial band topology along with magnetism leads to different novel quantum phases. When time-reversal symmetry is broken in three-dimensional topological insulators (TIs) through, e.g., the proximity effect, different phases such as the quantum Hall phase or the quantum anomalous Hall(QAH) phase emerge, displaying interesting transport properties for spintronic applications. The QAH phase displays sidewall chiral edge states, which leads to the QAH effect. We have considered a heterostructure consisting of a TI, namely BiSe, sandwiched between two two-dimensional ferromagnetic monolayers of CrI, to study how its topological and transport properties change due to the proximity effect. Combining DFT and tight-binding calculations, along with non-equilibrium Green’s function formalism, we show that a well-defined exchange gap appears in the band structure in which spin-polarised edge states flow. In a finite slab, the nature of the surface states depends on both the cross-section and thickness of the system. Therefore, we also study the width and finite-size effects on the transmission and topological properties of this magnetised TI nanoribbon.

Diminution of surface spin disorder in a ferromagnet via proximity effect of single-molecule magnets

Abstract Field-dependent resistance of a magnetic layer is often used as the basic tunable operational entity in several spintronics applications. In this work we demonstrate that the magnetoresistance (MR) of a classic ferromagnetic Ni layer can be tuned significantly by controlling the surface spin scattering of electrons, by manipulating disordered surface spins via proximity effect. This was achieved by drop casting molecules of a well-known single molecule magnet Mn 12-ac on micro-tracks of a thin (~12 nm) Ni film. We found significant changes in the width and sign of the magnetoresistance of the Ni micro-tracks. This is explained in the light of possible locking of the disordered surface spins of the Ni layer with the high spin moment of adjacent Mn 12-ac molecules, causing reduction in the surface spin scattering. As expected, the spin moments of Mn 12-ac molecules were found to effectively pin the surface spins only below the blocking temperature of Mn 12-ac. Above the blocking temperature, the Mn 12-ac molecules had no effect on the MR behavior of Ni micro-tracks. This observation offers a simple route to achieve on-demand low or high resistance states of a magnetic layer, very relevant to the field of spintronics.

Field-free ultrafast magnetization reversal of a nanodevice by a chirped current pulse via spin-orbit torque

We investigate the magnetization reversal of a perpendicularly magnetized nanodevice using a chirped current pulse (CCP) via spin-orbit torques (SOTs). Our numerically simulated findings demonstrate that both the field-like (FL) and damping-like (DL) components of SOT in CCP can be efficiently utilized to induce ultrafast magnetization reversal without any symmetry-breaking means. For a wide frequency range of the CCP, the minimal current density is significantly smaller compared to the current density of conventional SOT-reversal. This ultrafast reversal is achieved due to the CCP triggering enhanced energy absorption (emission) of the magnetization from (to) the FL- and DL-components of SOT before (after) crossing over the energy barrier. We also verify the robustness of the CCP-driven magnetization reversal at room temperature. Moreover, this strategy is applicable also to induce field-free ultrafast and efficient switching of perpendicular synthetic antiferromagnetic and ferrimagnetic (SFi) nanodevices. The minimal current density of deterministic switching of the SFi system decreases significantly with the reduction of one layer's magnetization, mainly because the SOT amplitude is inversely proportional to the saturation magnetization. Therefore, this study enriches the basic understanding of field-free SOT-reversal and provides a way to realize ultrafast SOT-MRAM devices with various free layer designs.

Programmable Magnetic Hysteresis in Orthogonally-Twisted 2D CrSBr Magnets via Stacking Engineering.

Twisting 2D van der Waals magnets allows the formation and control of different spin-textures, as skyrmions or magnetic domains. Beyond the rotation angle, different spin reversal processes can be engineered by increasing the number of magnetic layers forming the twisted van der Waals heterostructure. Here, pristine monolayers and bilayers of the A-type antiferromagnet CrSBr are considered as building blocks. By rotating 90 degrees these units, symmetric (monolayer/monolayer and bilayer/bilayer) and asymmetric (monolayer/bilayer) heterostructures are fabricated. The magneto-transport properties reveal the appearance of magnetic hysteresis, which is highly dependent upon the magnitude and direction of the applied magnetic field and is determined not only by the twist-angle but also by the number of layers forming the stack. This high tunability allows switching between volatile and non-volatile magnetic memory at zero-field and controlling the appearance of abrupt magnetic reversal processes at either negative or positive field values on demand. The phenomenology is rationalized based on the different spin-switching processes occurring in the layers, as supported by micromagnetic simulations. The results highlight the combination between twist-angle and number of layers as key elements for engineering spin-switching reversals in twisted magnets, of interest toward the miniaturization of spintronic devices and realizing novel spin textures.

Magneto-optical effects in the reflection and transmission of light for the case of an equatorially magnetized plate

Currently, expanding the elemental memory of computers and creating new generations of elemental bases for telecommunication systems are among the most important tasks for the national economy. However, further development of all these directions requires solving problems of a fundamental nature, such as achieving the superparamagnetic limit (which limits recording density), a relatively slow change in the magnetic state under the influence of magnetic field pulses (limiting recording speed), and a small magnitude of magneto-optical effects (limiting their use in integrated photonics). To solve these problems, the development and creation of new hybrid magnetic nanostructures that combine magnetic and non-magnetic materials - dielectrics, semiconductors, and metals - in various combinations is of particular relevance. In such structures, a significant enhancement of non-reciprocal linear and nonlinear optical and magneto-optical phenomena is possible, as well as the manifestation of new effects (for example, the effects of magneto-optical spatial dispersion). This article explores the reflection and transmission of light from a magnetic layer on a transparent (glass) substrate. As a result, formulas were obtained for the equatorial Kerr effect in reflected and transmitted light. These results are necessary for interpreting experimental data on the equatorial Kerr effect.

Aqueous Alteration as an Origin of Martian Magnetization

AbstractStrong magnetic fields have been measured from orbit around Mars over parts of the ancient southern highlands crust and on the surface at the InSight landing site. The geological processes that are responsible for generating strong magnetization within the crust remain poorly understood. One possibility is that intense aqueous alteration of crustal materials, through the process of serpentinization, could have produced magnetite that was magnetized in the presence of a global core‐generated magnetic field. Here, we test this idea with geophysical and geochemical models. We first determine the magnetizations required to account for the observed magnetic field strengths and then estimate the amount of magnetite necessary to account for these magnetizations. For the strongest orbital magnetic field strengths, about 7 wt% magnetite is required if the magnetic layer is 10 km thick. For the surface field strength observed at the InSight landing site, 0.4–1.1 wt% magnetite is required if the magnetic layer corresponds to one or more of the three crustal layers observed in the InSight seismic data (with thicknesses from 8 to 39 km). We then investigate the minerals that are produced by aqueous alteration for various possible crustal compositions and water‐to‐rock ratios using a thermodynamic model. Magnetite abundances up to 6 wt% can be generated for dunitic compositions that could account for the strongest magnetic anomalies. For more representative basaltic starting compositions, however, more than 0.4 wt% can only be generated when using high water‐to‐rock ratios, which could account for the weaker magnetizations beneath the InSight landing site.