Magnetic Nanostructures Research Articles

Magnetogenetics with Piezo1 Mechanosensitive Ion Channel for CRISPR Gene Editing.

Regulation of genetic activity in single cells and tissues is pivotal to determine key cellular functions in current biomedicine, yet the conventional biochemical activators lack spatiotemporal precision due to the diffusion-mediated slow kinetics and nonselectivity. Here, we describe a magnetogenetic method for target-specific activation of a clustered regularly interspaced short palindromic repeats (CRISPR) system for the regulation of intracellular proteins. We used magnetomechanical force generated by the magnetic nanostructure to activate pre-encoded Piezo1, the mechanosensitive ion channel, on the target cell. The activated Piezo1 further triggers the intracellular Ca2+ signaling pathway, inducing the pre-encoded genes to express genes of interest (GOIs), which is Cas9 protein for the CRISPR regulation of the target proteins. We demonstrated that this magnetogenetic CRISPR system successfully edits the target genome for both in vitro and pseudo-in vivo environments, providing a versatile magnetic platform for remote gene editing of animals with various size scales.

Micromagnetic Study on Branch Hybridizations of Spin-Wave Modes in Ferromagnetic Nanostrips.

Magnonics is an emerging field in spintronics, aiming at the development of new-concept magnetic devices processing information via the manipulation of spin waves (SWs) in magnetic nanostructures. One of the most popular SW waveguides exploited currently is ferromagnetic nanostrips. Due to quantization caused by the lateral confinements, the dispersion of SWs propagating in a strip is characterized by a multi-branched structure. Consequently, SWs excited in the system involve superpositions of degenerate modes from different branches of the dispersion curves. In this work, we theoretically study the SW branch hybridization effect for two types of excitation methods, either by using a local oscillating magnetic field or a fast-moving field pulse. The former is based on the resonance effect and the latter on the Cherenkov-like emission mechanism. Micromagnetic simulations yield a variety of SW profiles with rather complex structures, which can be well explained by mode superpositions. These results draw attention to the significance of the SW branch hybridization effect when dealing with SWs in nanostrips and provide new aspects for the manipulation of SWs.

The effect of surface plasmonic resonances on magneto-plasmonic spherical core-shell nanocomposites

In this study, the effect of plasmon resonance on magneto-plasmonic spherical core-shell nanocomposite enclosed in a dielectric host medium is theoretically investigated by applying electrostatic approximation (esa) and Maxwell-Garnet effective medium theories to obtain magneto-optical parameters such as; effective electric permittivity and magnetic permeability as well as the corresponding extinction cross-sections. Likewise, for a fixed size of QDs (of radius nm) numerical analysis was performed to determine the plasmonic resonance effect by varying the parameters such as the metal fraction (β) and the dielectrics (εh) of the host medium on the magneto-plasmonic nanostructures (nss). The results depict that graphs of absorption, scattering, and extinction cross-sections as a function of wavelength have two positions of resonance peaks. The first set of peaks are in the ultraviolet (uv) and the second located in visible regions. These peaks originated from the strong coupling between a regular periodic vibrations of surface plasmons of silver (Ag) with the excitonic state of the dielectric/semiconductor at the internal ( ) and external (Ag/host) interfaces. As β increases, the absorption and scattering cross-sections are blue-shifted in the first peak and red shifted the second set of peaks. Similarly, as εh increases or as β decreases, the sets of resonance peaks for extinction cross-section gets enhanced; while keeping one of these parametric quantities fixed at once. The resulting surface plasmon resonance effect might be utilized in a variety of applications that combines both the plasmonic and magnetic core-shell nanostructures ranging from UV to Visible spectral regions.

Exploring the Antibacterial Properties of Lignin-coated Magnetic Nanoparticles Synthesized in a One-pot Process†.

Given the current grave problems with antibiotic resistance, the discovery of novel, unconventional antibacterial drugs is not just important but also urgent. In this contribution, we report on the synthesis and testing of several composite nanomaterials that may find applications as therapeutic drugs or surface disinfectants. These materials are based on magnetic nanostructures coated with lignin, for example, lignin@FeCo. The magnetic properties of these nanocomposites facilitate removal or localization, whereas the lignin shell provides biocompatibility. These nanomaterials are mild antibacterials in the absence of light, but when illuminated become powerful antibacterial agents with typically ≥6 log units of bacterial reduction in 1-5 min of irradiation. These materials are strongly absorbing, including in the very useful NIR biological window, which we illustrate using 810 nm LED irradiation. We also show that in the short time required for antibacterial action, thermal changes are very small (≤5°C). Further, biocompatibility tests using fibroblasts show very limited cell damage and no enhanced adverse effect during 810 nm NIR illumination. As a surface coating for the active material, lignin provides a "trojan horse" strategy to facilitate the antibacterial action.

Synthesis of magneto-plasmonic hybrid material for cancer hyperthermia

Magnetic nanoparticle CoFe2O4-based hyperthermia is a promising non-invasive approach for cancer therapy. However, CoFe2O4 nanoparticles (NPs) have a low heat transfer efficiency, which limits their practical clinical applications. Hence, it is necessary to investigate the higher-performance magnetic NPs-based hybrid nanostructures to enhance their magnetic hyperthermia efficiency. This work presents a facile in situ approach for synthesizing cobalt ferrite (CoFe2O4) silver (Ag) hybrid NPs as optical-magnetic hyperthermia heat mediators. The prepared cobalt ferrite silver hybrid NPs exhibit a higher heat generation than that of individual Ag or CoFe2O4 NPs under simultaneous exposure to an alternating current magnetic field and laser source. The obtained results confirm that the hybridization of CoFe2O4 and Ag NPs could significantly enhance the hyperthermia efficiency of the prepared NPs. Therefore, the CoFe2O4-Ag hybrid NPs are considered as potential candidates for a high-performance hyperthermia mediator based on a simple and effective synthesis approach.

Editorial: Generation, detection and manipulation of skyrmions in magnetic nanostructures

Editorial: Generation, detection and manipulation of skyrmions in magnetic nanostructures

Magnetic Coconut Shell‐Derived Activated Carbon Adorned with Cu2O Nanoparticles: A Green and Efficient Porous Catalyst for N‐Arylation of Hetero‐Aromatics in Eutectic Medium

AbstractIn the current research, a green, robust, and economical metal oxide‐based nanocatalyst has been developed by functionalization of coconut shell‐derived mesoporous activated carbon with magnetically separable amino acid and subsequent decoration with Cu2O nanoparticles (Fe3O4@L‐arginine‐AC−Cu2O). This magnetic nanostructure was analyzed by different techniques including FT‐IR, FE‐SEM, EDX/MAP, XRD, TEM, TGA, VSM, BET, and ICP‐OES. The catalytic efficiency of the nanoparticles was studied in Ullmann N‐arylation reaction of some N‐heterocycle compounds including indole, imidazole, and pyrrole with various aryl halides in choline chloride/glycerol (1 : 2), which is a green and biomass‐based deep eutectic solvent (DES). The reaction proceeded smoothly and the desired N‐arylation products were obtained in good to excellent yields (75‐96 %). Notably, the magnetic porous nanocatalyst can be easily separated and reused at least six times without a notable decrease in its performance. The solvent is also able to recover, thereby increasing the attractiveness of this approach. In other words, this approach can serve to significantly expand the scope of the C−N coupling products for their applications in further studies.

Transmission magneto-optics in multilayers at transverse magnetization

Transverse magneto–optic (MO) effect in transmission (TMOET) in multilayers presents interest in the studies of interfaces in magnetic nanostructures and in the design of nonreciprocal devices and magnetic sensors. It can be used as an easily accessible characterization tool for layered nanostructures with antiferromagnetic ordering considered for antiferromagnetic spintronics. TMOET can provide the information on magnetic structure with sub-nanometer resolution in a dynamic regime up to THz frequencies. The approach is illustrated on TMOET in multilayered Fe/AlN systems at a radiation wavelength of 410 nm. TMOET distinguishes between parallel and antiparallel orientation of magnetic moments in layered nanostructures and can be made stronger at antiparallel orientation of magnetic moments. The TMOET response can be optimized by sandwiching the magnetic film with dielectrics and exploited in sensors of high frequency electromagnetic fields.

High-frequency modes in a magnetic buckyball nanoarchitecture

Artificially fabricated three-dimensional magnetic nanostructures have recently emerged as a new type of magnetic material with the potential of displaying physical properties absent in thin-film geometries. Interconnected nanowire arrays yielding three-dimensional versions of artificial spin-ices are of particular interest within this material category. Despite growing interest in the topic, several properties of these systems are still unexplored. Here, we study, through micromagnetic simulations, the high-frequency dynamic modes developing in buckyball-type magnetic nanoarchitectures. We obtain a characteristic excitation spectrum and analyze the corresponding mode profiles and their magnetic field dependence. The magnetic resonances are localized at different geometric constituents of the structure and depend on the local magnetic configuration. These features foreshow the potential of such systems for reprogrammable magnonic device applications with geometrically tunable frequencies.

Combining two-photon lithography with laser ablation of sacrificial layers: A route to isolated 3D magnetic nanostructures

Three-dimensional (3D) nanostructured functional materials are important systems allowing new means for intricate control of electromagnetic properties. A key problem is realising a 3D printing methodology on the nanoscale that can yield a range of functional materials. In this article, it is shown that two-photon lithography, when combined with laser ablation of sacrificial layers, can be used to realise such a vision and produce 3D functional nanomaterials of complex geometry. Proof-of-principle is first shown by fabricating planar magnetic nanowires raised above the substrate that exhibit controlled domain wall injection and propagation. Secondly, 3D artificial spin-ice (3DASI) structures are fabricated, whose complex switching can be probed using optical magnetometry. We show that by careful analysis of the magneto-optical Kerr effect signal and by comparison with micromagnetic simulations, depth dependent switching information can be obtained from the 3DASI lattice. The work paves the way for new materials, which exploit additional physics provided by non-trivial 3D geometries.

Maneuvering the magnetic anisotropy in single-phase nanocrystalline α-FeCo via external static magnetic field assisted one dimensional growth

Magnetic anisotropy in magnetic nanostructures is highly desirable for the manufacturing of magnetic data storage devices. Therefore, in the present work, the effective magnetic anisotropy is investigated in α-FeCo nanoparticles (NPs) and nanowires (NWs) prepared using hydrazine reduction method. The growth of the NWs was manifested by applying external static magnetic field using bar magnets during synthesis which promoted the continuous growth up to 4 µm of average length and an average diameter of ~ 294 nm. The NP-formation as well as NW-growth adopted the phenomena of Ostwald ripening. The NWs demonstrated the enhanced saturation magnetization, enhanced effective magnetic anisotropy and reduced coercivity as compared to the corresponding NPs. The enhanced magnetic properties of the NWs have been associated with the magnetic force exerted by the external magnetic field during growth which aligned the crystallites along the direction of magnetic field together with the reorientation of the easy axis< 100 > of FeCo along the long axis of the wire. The assistance of the magnetic field during growth enhanced the ease of magnetization along the long axis of the wire. Additionally, the growth induced shape magnetic anisotropy via induced the dipolar interactions lead to the enhanced effective magnetic anisotropy. Thereby, it can be suggested that the external magnetic field applied during synthesis not only plays a primary role in the growth of NWs but also enhances the intrinsic magnetic properties of the material.

Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size.

The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.

Observation of Néel-type skyrmions in acentric self-intercalated Cr1+δTe2

Transition-metal dichalcogenides intercalated with 3d-transition metals within the van der Waals (vdW) gaps have been the focus of intense investigations owing to their fascinating structural and magnetic properties. At certain concentrations the intercalated atoms form ordered superstructures that exhibit ferromagnetic or anti-ferromagnetic ordering. Here we show that the self-intercalated compound Cr1+δTe2 with δ ≈ 0.3 exhibits a new, so far unseen, three-dimensionally ordered (2×2×2) superstructure. Furthermore, high resolution X-ray diffraction reveals that there is an asymmetric occupation of the two inequivalent vdW gaps in the unit cell. The structure thus lacks inversion symmetry, which, thereby, allows for chiral non-collinear magnetic nanostructures. Indeed, Néel-type skyrmions are directly observed using Lorentz transmission electron microscopy. The skyrmions are stable within the accessible temperature range (100–200 K) as well as in zero magnetic field. The diameter of the Néel skyrmions increases with lamella thickness and varies with applied magnetic field, indicating the role of long-range dipole fields. Our studies show that self-intercalation in vdW materials is a novel route to the formation of synthetic non-collinear spin textures.

(Invited) Magneto-Ionic Control of Heterostructures and Interfaces

Magneto-ionics has shown promise for energy-efficient nanoelectronics, where ionic migration can be used to achieve atomic scale control of interfaces in magnetic nanostructures, and in turn modulate a wide variety of functionalities. Recently, we have discovered that chemisorbed oxygen and hydrogen on the surface of ferromagnetic films can induce significant Dzyaloshinskii–Moriya interaction (DMI) [1], a handle to introduce topology into nanoscale magnets. This has enabled direct tailoring of skyrmions winding number as well as wall type at room temperature via oxygen chemisorption. We have also demonstrated a sensitive and reversible chirality switching of magnetic domain walls [2] and writing/deleting of skyrmions [3] via hydrogen chemisorption/desorption. These chemisorption induced magnetic effects on controlled ferromagnet surfaces offer an ideal platform to gain quantitative understanding of magneto-ionics at buried interfaces, where the ionic motion can be further controlled by an electric field [4]. These effects are relevant for 3-dimensional information storage as a potentially contactless way to address spin textures, such as in interconnected nanowire networks [5]. Interestingly, nanoporous metal foams made of random assemblies of nanowires have found applications in deep-submicron particulate filtration, relevant to combatting COVID-19 and air pollution. Such foams are efficient, breathable, light-weight, robust, and can be reused and recycled [6]. Our mask design based on such foams has been selected by BARDA-NIOSH as a Phase 1 Winner of the Mask Innovation Challenge [7].[1] Science Advances, 6, eaba4924 (2020).[2] Physical Review X, 11, 021015 (2021).[3] DOI: https://doi.org/10.21203/rs.3.rs-575830/v1[4] ACS Applied Materials and Interfaces, 13, 38916−38922 (2021).[5] Nano Letters, 21, 716-722 (2021).[6] Nano Letters, 21, 2968-2974 (2021).[7] https://drive.hhs.gov/mask_challenge.html.This work has been supported by the NSF (DMR-1905468, DMR-2005108, ECCS-1933527), the nCORE SMART center through SRC/NIST, the University of California and Georgetown University.

Unveiling the Complex Magnetization Reversal Process in 3D Nickel Nanowire Networks

AbstractUnderstanding the interactions among magnetic nanostructures is one of the key factors to predict and control the advanced functionalities of 3D integrated magnetic nanostructures. In this work, the focus is on different interconnected Ni nanowires forming an intricate, but controlled, and ordered magnetic system: Ni 3D Nanowire Networks (3DNNs). These self‐ordered systems present striking anisotropic magnetic responses, depending on the interconnections’ position between nanowires. To understand their collective magnetic behavior, the magnetization reversal processes are studied within different Ni 3D Nanowire Networks compared to the 1D nanowire 1DNW array counterparts. The systems are characterized at different angles using first magnetization curves, hysteresis loops, and First Order Reversal Curves techniques, which provided information about the key features that enable macroscopic tuning of the magnetic properties of the 3D nanostructures. In addition, micromagnetic simulations endorse the experiments, providing accurate modeling of their magnetic behavior. The results reveal a plethora of magnetic interactions, neither evident nor intuitive, which are the main role players controlling the collective response of the system. The results pave the way for the design and realization of 3D novel metamaterials and devices based on the nucleation and propagation of ferromagnetic domain walls both in 3D self‐ordered systems and future nano‐lithographed devices.

Bio-inspired computing with magnetic skyrmions using deep learning

Spintronic systems demonstrate significant value due to variety of features that can be used in bio-inspired computing applications. Skyrmion is a magnetic nanostructure which can be used as an information carrier. In this paper, we simulate vortex-free Gaussian wave packet by incorporating spin–orbit coupling (SoC) into three-component Bose–Einstein condensates (BECs). We next observe that skyrmions can be naturally generated from vortex-free Gaussian wave packet, further these structurally asymmetric devices are constructed and initial device classifications are carried out. A spin device consisting of vertically-stacked multiple skyrmions is proposed termed as skyrmion spintronic synapse (SkSS) and skyrmion spintronic Neuron (SkSN). This paper depicts training the neural network with surrogate gradients with deep learning strategies using topologically nontrivial spin textures. The current popular Graphics Processing Unit (GPU)-based neural network computations are compared with the proposed method. This research paves a way for a neuromorphic computing systems on exotic topological solitons.

High Spin Hall Conductivity Induced by Ferromagnet and Interface

AbstractSpin‐orbit‐torque (SOT) offers a highly attractive perspective for manipulating magnetization dynamics in magnetic nanostructures. SOT is been observed and studied in various systems. However, limited by the efficiency, SOT‐induced switching of the ultrahard ferromagnet is still extremely difficult and a further improvement in efficiency is requested. Here, the SOT is reported in chemically disordered soft Fe0.5Pt0.5 and Pt/Fe0.5Pt0.5 bilayers. Due to the magnetization‐strengthened spin Hall effect, the damping‐like torque efficiency and spin Hall conductivity (SHC) in Fe0.5Pt0.5 reach 1.11 and 1.08 × 106 ℏ/2e Ω−1 m−1 respectively, much higher than those in conventional materials. Furthermore, the Pt/Fe0.5Pt0.5 interface enhances SHC to a total of 2.93 × 106 ℏ/2e Ω−1 m−1 due to the interfacial symmetry breaking. This system can be used to partially switch the magnetization of ultra‐hard exchange‐spring system with a switching field of 1T by applying a relatively low current. This finding will push forward the development of SOT devices with ultrahigh‐density and low‐power consumption.

Green synthesis of spinel copper ferrite (CuFe2O4) nanoparticles and their toxicity

Abstract In this study, magnetic spinel copper ferrite (CuFe2O4) nanostructures were eco-friendly synthesized using Nasturtium officinale extract. Physicochemical properties of these nanostructures were determined by transmission electron microscopy, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometry, and energy dispersive X-ray mapping analysis. XRD patterns conform to the CuFe2O4 formation. SEM results demonstrated ceramic spinel CuFe2O4 nanostructures with spherical surface morphologies. The cytotoxicity effect of CuFe2O4 nanostructures against rat pheochromocytoma (PC12) cells was evaluated based on MTT assay. The magnetic nanostructures had low toxicity at a concentration of 250 µg/mL. It appears that these nanostructures can be considered as suitable candidates for drug delivery and other biomedical applications, because of their low toxicity effects.

Magnetic force microscopy of an operational spin nano-oscillator

Magnetic force microscopy (MFM) is a powerful technique for studying magnetic microstructures and nanostructures that relies on force detection by a cantilever with a magnetic tip. The detected magnetic tip interactions are used to reconstruct the magnetic structure of the sample surface. Here, we demonstrate a new method using MFM for probing the spatial profile of an operational nanoscale spintronic device, the spin Hall nano-oscillator (SHNO), which generates high-intensity spin wave auto-oscillations enabling novel microwave applications in magnonics and neuromorphic computing. We developed an MFM system by adding a microwave probe station to allow electrical and microwave characterization up to 40 GHz during the MFM process. SHNOs—based on NiFe/Pt bilayers with a specific design compatible with the developed system—were fabricated and scanned using a Co magnetic force microscopy tip with 10 nm spatial MFM resolution, while a DC current sufficient to induce auto-oscillation flowed. Our results show that this developed method provides a promising path for the characterization and nanoscale magnetic field imaging of operational nano-oscillators.

Synthesis of magnetic polypyrrole modified sodium alginate nanocomposite with excellent antibacterial properties and optimization of dye removal performance using RSM

In this study, a novel polypyrrole/Sodium-Alginate/CuFe2O4 magnetic nanostructure (PPy/NA-Alg/CuFe2O4) was synthesized by the hydrothermal route and used as an adsorbent in order to eliminate Direct Blue 199 (DB199) dye from wastewater. The characterization of the synthesized PPy/NA-Alg/CuFe2O4 was confirmed by investigation of SEM, TEM, FTIR, XRD, and VSM analyses. Five significant operational parameters including initial dye concentration (20–100 mg/L), temperature (25–45 °C), the dose of adsorbent (2–22 mg), contact time (10-210 min), and pH (2-10) were optimized to achieve the greatest removal efficiency of DB199 by a central composite rotatable design (CCRD) combined with response surface methodology (RSM). A high coefficient of determination (R2 = 0.99) was calculated by analysis of variance (ANOVA). Under optimal conditions, adsorption dosage = 7.00 mg, temperature = 30.61 °C, initial concentration = 80.00 mg/L, pH = 4.00 and contact time = 159.42 min, the maximum adsorption capacity of the adsorbent (80.36) was highly matched with the predicted response values, illustrating the appropriate of RSM in optimum conditions. The experimental data were matched well to the Langmuir isotherm model and both pseudo-first-order and pseudo-second-order kinetics. Additionally, thermodynamic parameters exhibited spontaneous nature and exothermic reaction. Adsorption–desorption experiments evidenced that the PPy/NA-Alg/CuFe2O4 synthesized could be used for up to three successive adsorption cycles. Furthermore, the nanocomposite showed strong antibacterial activity against two model microorganisms, one gram-negative (Escherichia coli) and one gram-positive (Staphylococcus aureus) via disc diffusion and linear cultivation methods.