NiFe Layer Research Articles

Anisotropic magnetoresistance probed by non-resonant microwave absorption in exchange-biased NiFe/IrMn structures

Sharp change of non-resonant microwave absorption was found in exchange-biased NiFe/IrMn and NiFe/Cu/IrMn structures possessing anisotropic magnetoresistance (AMR) and planar Hall effect (PHE). Angular dependence of the microwave detected AMR and contribution of the domain expansion to AMR microwave signal were analyzed. Decrease in the microwave absorption signal caused by Cu spacer between ferromagnetic NiFe and antiferromagnetic IrMn layers was observed, when NiFe and IrMn layers become exchange decoupled. Additional characterization of the electric transport was proved by asymmetry of resonant line. Sensitivity of the microwave AMR method is enough high to detect magnetic fields of microTesla level, that provides remote detection with a sensitivity corresponding to standard galvanic sensors. Developed technique is promising for wireless AMR sensor technology providing coordinate and angular field measurements through remote microwave absorption.

Interface-Engineered NiFe/Ni-S Nanoparticles for Reliable Alkaline Oxygen Production at Industrial Current: A Sulfur Source Confinement Strategy.

Using powder-based ink appears to be the most suitable candidate for commercializing the membrane electrode assembly (MEA), while research on the powder-based NPM catalyst for anion exchange membrane water electrolyzer (AEMWE) is currently insufficient, especially at high current density. Herein, a sulfur source (NiFe Layered double hydroxide adsorbed ) confinement strategy is developed to integrate Ni3S2 onto the surface of amorphous/crystalline NiFe alloy nanoparticles (denoted NiFe/Ni-S), achieving advanced control over the sulfidation process for the formation of metal sulfides. The constructed interface under the sulfur source confinement strategy generates abundant active sites that increase electron transport at the electrode-electrolyte interface and improve ability over an extended period at a high current density. Consequently, the constructed NiFe/Ni-S delivers an ultra-low overpotential of 239mV at 10mA cm-2 and 0.66mA under an overpotential of 300mV. The AEMWE with NiFe/Ni-S anode exhibits a cell voltage of 1.664V @ 0.5 A cm-2 and a 400h stability at 1.0Acm-2.

Tungstate Intercalated NiFe Layered Double Hydroxide Enables Long-Term Alkaline Seawater Oxidation.

Renewable electricity-driven seawater splitting presents a green, effective, and promising strategy for building hydrogen (H2)-based energy systems (e.g., storing wind power as H2), especially in many coastal cities. The abundance of Cl- in seawater, however, will cause severe corrosion of anode catalyst during the seawater electrolysis, and thus affect the long-term stability of the catalyst. Herein, seawater oxidation performances of NiFe layered double hydroxides (LDH), a classic oxygen (O2) evolution material, can be boosted by employing tungstate (WO4 2-) as the intercalated guest. Notably, insertion of WO4 2- to LDH layers upgrades the reaction kinetics and selectivity, attaining higher current densities with ≈100% O2 generation efficiency in alkaline seawater. Moreover, after a 350h test at 1000mAcm-2, only trace active chlorine can be detected in the electrolyte. Additionally, O2 evolution follows lattice oxygen mechanism on NiFe LDH with intercalated WO4 2-.

Magnon-mediated spin Hall magnetoresistance and unidirectional magnetoresistance in Pt/NiO/NiFe structures

Spin–orbit torque provides an efficient strategy for electric manipulation of magnetization. However, Joule heat accompanying with electron motion in the electron-mediated spin current result in unavoidable power dissipation. Moreover, the spin diffusion length in electron-mediated spin current is relatively short, preventing the transmission of spin information over long distances. Magnon-mediated spin current, without moving electrons, can be an excellent alternative to the conventional spin current. Magnon-mediated transfer torque effect has been reported in several previous works. Here, we report the magnon-mediated spin Hall magnetoresistance (SMR) and unidirectional magnetoresistance (UMR) in Pt/NiO/NiFe structures. The significant SMR and UMR were observed in the samples with the NiO thickness up to 60 nm, demonstrating the efficient transmission of magnon-mediated spin current over long distances in the NiO layer. In addition, we observed current-induced in-plane magnetization switching in the NiFe layer via the UMR measurement. These results demonstrated the possibility for developing the efficient spintronic devices operated by magnons.

Effective Influence of an Electric Current on Brillouin Spectra in the NiFe/IrMn Structure

When an electric current flows through the NiFe/IrMn structure, a significant redistribution of the intensities of the direct Stokes and inverse anti-Stokes lines in spectra of Brillouin scattering on thermal spin waves is observed. This is due to a change in the orientation of uniaxial anisotropy and the corresponding easy axis of the exchange shift under the action of the spin–orbit torque in the IrMn antiferromagnet, which in turn affects the dynamics of spin waves in the neighboring ferromagnetic NiFe layer. The detected effect indicates that spin-wave processes in a ferromagnet can be controlled by applying a spin current to change the magnetic anisotropy of the NiFe/IrMn interface.

Stable and active methanol oxidation via anchored PtRu alloy nanoparticles on NiFe layered double hydroxides

Enhancing the catalytic efficiency of the methanol electro-oxidation reaction (MOR) holds paramount importance in expediting the commercialization of direct methanol fuel cells (DMFCs).

Electrochemical microfluidic paper-based analytical device for label-free detection of SARS-CoV-2 antigen by LDH redox probe

In the offered study, the proposed sensor combined the innovative disposable microfluidic paper-based immunosensor and cost-effective plant-based anti-SARS-CoV-2 monoclonal antibody CR3022, expressed in Nicotiana benthamiana. An electrochemical microfluidic paper-based analytical device (µPAD) was introduced for quantitative detection of the SARS-CoV-2 antigen employing electrocatalytic activity of the Ni Fe layered double hydroxide (NiFe LDH). Its electrocatalytic activity asthe platform of proposed the analytical device enhanced the signal output via redox-recycling of the species the ferri/ferrocyanide [Fe(CN)6]3-/4- in solution and is applied to µPAD response signal. Layered NiFe double hydroxide (LDH) nanosheets with a suitable redox potential were prepared by incorporating Fe into the Ni-based LDH. With the help of Fe, the charge-transfer kinetics for the reduction of Ni3+ to Ni2+ was improved and the formation of unwanted Ni components with higher oxidation state was suppressed. The incorporated Fe as the electron transfer mediator enhanced the process of Ni(OH)2/NiOOH redox cycle. Under the optimum conditions, the dependency of impedance signal and SARS-CoV-2 concentration showed a linear region from 10 fg/mL-5 ng/mL with a detection limit of 0.23 fg/mL. This Paper-based immunosensor device also showed long stability and good reproducibility, which can be used for the quantitative assay of the SARS-CoV-2. The results of nasal samples analysis revealed the applicability of the resulting biosensor.

Magnetic-Proximity-Induced Efficient Charge-to-Spin Conversion in Large-Area PtSe2/Ni80Fe20 Heterostructures.

As a topological Dirac semimetal with controllable spin-orbit coupling and conductivity, PtSe2, a transition-metal dichalcogenide, is a promising material for several applications, from optoelectrics to sensors. However, its potential for spintronics applications has yet to be explored. In this work, we demonstrate that the PtSe2/Ni80Fe20 heterostructure can generate large damping-like current-induced spin-orbit torques (SOT), despite the absence of spin-splitting in bulk PtSe2. The efficiency of charge-to-spin conversion is found to be -0.1 ± 0.02 nm-1 in PtSe2/Ni80Fe20, which is 3 times that of the control sample, Ni80Fe20/Pt. Our band structure calculations show that the SOT due to PtSe2 arises from an unexpectedly large spin splitting in the interfacial region of PtSe2 introduced by the proximity magnetic field of the Ni80Fe20 layer. Our results open up the possibilities of using large-area PtSe2 for energy-efficient nanoscale devices by utilizing proximity-induced SOT.

Tuning magnon spectra via interlayer coupling in pseudo-3D nanostructured artificial spin ice arrays

We have investigated the static and dynamic behavior of “pseudo-3D” trilayer square artificial spin ice structures. The trilayer stack comprises of two ferromagnetic Ni81Fe19 (Permalloy, Py) layers with 30 and 70 nm thickness, separated by a nonmagnetic copper layer of varying thickness from 2 to 40 nm. We show that the copper thickness enables interlayer coupling between layers to be finely controlled, leading to bespoke magnetization states and resonance spectra tuning. Our results demonstrate a further route to control the interaction in artificial spin ices beyond planar structures, enabling tunable magnetization dynamics, a potentially programmable degree of freedom for magnonic and microwave devices.

The Ni(OH)2 interlayer modified spherical NiFe layered double hydroxides for enhanced alkaline oxygen evolution reaction performance

Heterogeneous interface engineering is an ideal technique for the rational design of efficient and low-cost electrocatalysts for oxygen evolution reactions (OER). In this study, a complex hydrothermal-electrodeposition composite approach was used to insert a Ni(OH)2 interlayer into the tiny gaps between the layers of NiFe layered double hydroxides (NiFe LDHs), and the interlayer's influence on OER performance was examined. Benefiting from the support of Ni(OH)2 interlayer, the resulting Ni(OH)2/NiFe LDHs could withstand 5000 CV-AST tests with just a 6 mV overpotential increase, as well as 50 h of long-term operation with negligible activity loss on a potential of 1.724 VRHE. Meanwhile, in the OER process, the Ni(OH)2/NiFe LDHs exhibit 220 mV overpotential and 48.5 mV dec−1 Tafel slope in 1 M KOH solution, which is superior to NiFe LDHs, RuO2, and IrO2. Additionally, Ni(OH)2/NiFe LDHs show a high-polarization-potential stability during i-t tests. At 1.824 VRHE, the Ni(OH)2/NiFe LDHs could afford 12 h operation with ∼0.35 % activity loss, which was better than on a low potential of 1.624 VRHE (12 h, ∼8.4 % activity loss). This composite strategy may provide an effective method for optimizing other LDHs, as well as a new route for building high-activity and durable OER catalysts for practical water splitting.

Outstanding oxygen evolution reaction properties released at the interface of NiMoO4 and FeNi layer double hydroxide heterostructures

For the alkaline oxygen evolution reaction (OER), FeNi layered double hydroxide (FeNi LDH) exhibits good activity and stability. For the sake of saving freshwater, the use of abundant seawater as an electrolyte poses new requirements for its OER performance. A novel method was designed based on a corrosion reaction to convert commercial Fe foam into a high-performance OER catalyst (FeNiM), which consisted of FeNi LDH layers and NiMoO4 nanoparticles modified on its surface. FeNiM exhibited excellent OER activity, only requiring an overpotential of 250 mV to achieve a current density of 100 mA cm−2. Experimental results indicated that the heterostructures formed by NiMoO4 and FeNi LDH was conducive to exposing active sites, promoting the adsorption of active intermediates, and generating highly active oxyhydroxides. In addition, the heterostructure was beneficial to stabilizing the electrode surface structure and inhibiting seawater corrosion. Therefore, FeNiM could maintain high current density activity in both alkaline freshwater and alkaline seawater, which only required low overpotentials of 326 mV and 304 mV to achieve a high current density of 1500 mA cm−2, respectively. This catalyst preparation method has the advantages of economic efficiency, industrial compatibility, and significantly promoting the development of green hydrogen economy and industrial seawater desalination.

Intrabasal Plane Defect Formation in NiFe Layered Double Hydroxides Enabling Efficient Electrochemical Water Oxidation.

Defect engineering has proven to be one of the most effective approaches for the design of high-performance electrocatalysts. Current methods to create defects typically follow a top-down strategy, cutting down the pristine materials into fragmented pieces with surface defects yet also heavily destroying the framework of materials that imposes restrictions on the further improvements in catalytic activity. Herein, we describe a bottom-up strategy to prepare free-standing NiFe layered double hydroxide (LDH) nanoplatelets with abundant internal defects by controlling their growth behavior in acidic conditions. Our best-performing nanoplatelets exhibited the lowest overpotential of 241 mV and the lowest Tafel slope of 43 mV/dec for the oxygen evolution reaction (OER) process, superior to the pristine LDHs and other reference cation-defective LDHs obtained by traditional etching methods. Using both material characterization and density functional theory (DFT) simulation has enabled us to develop relationships between the structure and electrochemical properties of these catalysts, suggesting that the enhanced electrocatalytic activity of nanoplatelets mainly results from their defect-abundant structure and stable layered framework with enhanced exposure of the (001) surface.

The noncollinear interlayer coupling in NiFe/NiO/NiFe trilayers

The interlayer coupling and magnetization reversal behaviors in NiFe/NiO/NiFe trilayers were investigated using polarized neutron reflectivity and Monte Carlo (MC) simulations. Our results reveal that the shape of NiFe loops transitions from square to tilted as the NiO thicknesses decrease, indicating changes in the direction of NiFe layer’s easy axis. This phenomenon can be attributed to variations occurring at NiO/NiFe interfaces for different NiO layer thicknesses. With thin NiO layer, interdiffusion at the NiO/NiFe interfaces leads to frustrated coupling, resulting in a noncollinear interlayer coupling. This observation is supported by MC simulations. Conversely, hardly any coupling frustration is observed for the sample with a thick NiO layer. Our findings propose a novel way to tailor the interlayer coupling through interface engineering.

De-Pinning Fermi Level and Accelerating Surface Kinetics with an ALD Finish Boost the Fill Factor of BiVO4 Photoanodes to 44.

With the rapid development of performance and long-term stability, bismuth vanadate (BiVO4 ) has emerged as the preferred photoanode in photoelectrochemical tandem devices. Although state-of-the-art BiVO4 photoanodes realize a saturated photocurrent density approaching the theoretical maximum, the fill factor (FF) is still inferior, pulling down the half-cell applied bias photon-to-current efficiency (HC-ABPE). Among the major fundamental limitations are the Fermi level pinning and sluggish surface kinetics at the low applied potentials. This work demonstrates that the plasma-assisted atomic layer deposition technique is capable of addressing these issues by seamlessly installing an angstrom-scale FeNi-layer between BiVO4 and electrolyte. Not only this ultrathin FeNi layer serves as an efficient OER cocatalyst, more importantly, it also effectively passivates the surface states of BiVO4 , de-pins the surface Fermi level, and enlarges the built-in voltage, allowing the photoanode to make optimal use of the photogenerated holes for achieving high FF up to 44% and HC-ABPE to 2.2%. This study offers a new approach for enhancing the FF of photoanodes and provides guidelines for designing efficient unassisted solar fuel devices.

Multilayering FeGa with NiFe and Al2O3 to enhance the soft magnetic properties

In this study, the impact of insulating Al2O3 interlayers on the static and dynamic magnetic properties of FeGa/NiFe multilayers was investigated. A multilayer structure consisting of ten (10 nm FeGa)/(2.5 nm NiFe) bilayers was first established to show a reduction in coercivity and high frequency losses compared to a single (100 nm FeGa)/(2.5 nm NiFe) bilayer, which itself shows better performance than a single 100 nm FeGa film. By strategically placing 2.5 nm Al2O3 interlayers in the FeGa/NiFe multilayers (after the FeGa layer but before the next NiFe layer), the composite displayed a reduced coercivity down to 3 Oe while retaining a strong uniaxial anisotropy. Due to the effectiveness of these ultra-thin Al2O3 layers in reducing the eddy current losses across the FeGa/NiFe multilayer stack, this multilayer structure exhibited excellent performance at high frequency, including a gilbert damping coefficient of 0.0081 and an inhomogeneous linewidth of 38 Oe. These results demonstrate that Al2O3 interlayers can improve the soft magnetic properties of (FeGa/NiFe)-based multilayers to enable integration in magnetoelastic and high frequency applications.

Influence of a Thin V2O3 Spacer on Interlayer Interactions in Fe-Ni/V2O3/FeNi Film Structures

In this paper, we explore the suggestions of the results of experimental studies on low-dimensional layered systems in FeNi/V2O3/FeNi film structures. The multifunctional material V2O3 is used as an interlayer between the magnetically active FeNi layers. The films were obtained by ultrahigh vacuum magnetron sputtering on a glass substrate with a base size of 10−10 Torr. It has been found that for V2O3 films, the decrease in the metal–semiconductor transition temperature increases significantly. Magnetic characteristics were studied on the MPMS-XL SQUID magnetometer. The exchange effect occurs both in the region where the oxide has a magnetic order and in the paramagnetic region. The latter is due to the effect of the magnetic panel in the oxide package. The phenomenon of oscillation of the exchange field occurs depending on the phenomenon of intermediate observation observed experimentally.

Tribocorrosion Behavior of γ′-Fe4N Nitride Layer Formed on Mild Steel by Plasma Nitriding in Chloride-Containing Solution

Nitriding has long been used to engineer the surfaces of engineering steels to improve their surface and subsurface properties. The role of the surface compound layer (γ′-Fe4N and/or ε-Fe2-3N) in improving the tribological and corrosion-resistant properties of nitrided steels has been established. However, there have been very few studies on the response of the compound layer to tribocorrosion in corrosive environments. In this work, the tribocorrosion behavior of a 5 μm thick γ′-Fe4N nitride layer produced on mild steel (MS) by plasma nitriding has been studied in a NaCl-containing solution under various electrochemical conditions. The results show that at a cathodic potential of −700 mV (saturated calomel electrode, SCE), where mechanical wear is predominant, the total material removal (TMR) from the γ′-Fe4N layer is 37% smaller than that from the untreated MS, and at open circuit potential, TMR from the layer is 34% smaller than that from the untreated MS, while at an anodic potential of −200 (SCE), the γ′-Fe4N layer can reduce TMR from mild steel by 87%. The beneficial effect of the γ′-Fe4N nitride layer in improving the tribocorrosion behavior of mild steel is derived from its high hardness and good corrosion resistance in the test solution and its ability to resist both mechanical wear and corrosion and to reduce wear–corrosion synergism.

NiFe/FeMn exchange biased systems for bias-field-free magnetization dynamics

The exchange bias phenomenon across a ferromagnet/antiferromagnet interface is of great interest in any spin valve type spintronics device. Here, we show a significant exchange bias effect in Ni80Fe20/Fe50Mn50 systems in the absence of any external field during the thin film growth. The effect of Ni80Fe20 thickness and the application of angular field on hysteresis loops are investigated. Magnetization dynamics using the ferromagnetic resonance technique have been investigated for the understanding of the interfacial properties. Both the hysteresis and the magnetization dynamics data reveal the presence of uniaxial anisotropy, which decreases with increasing the thickness of the Ni80Fe20 layer. Further investigation of the magnetic damping properties indicates the role of the seed layer in addition to the exchange bias effect. The results have potential implications for the development of self-biased systems that support magnetic oscillations and spin-wave-based information propagation without any external bias magnetic field.

Electroactivity Variable Valence NiFe Layered Double Hydroxyde for Cl− Removal through Electrically Switched Ion Exchange

AbstractNiFe layered double hydroxide (LDH) films with different Ni/Fe molar ratios were successfully prepared on carbon paper (CP) by the potentiostatic method and were used for the removal of chloride ions (Cl−) by electrically switched ion exchange (ESIX) technology. The results showed that the Ni/Fe ratios had a significant effect on the adsorption performance of LDH for Cl−. The prepared NiFe LDH film with Ni/Fe molar ratio of 1 : 1 showed the best Cl− ESIX performance and the maximum adsorption capacity could reach 43.8 mg ⋅ g−1 at 1.4 V (vs. SCE) in 20 ppm Cl− solution. The excellent adsorption performance of LDH for Cl− was mainly due to the coupling of the interlayer anion exchange mechanism and the electroactivity‐variable valence mechanism. In addition, the Cl− regeneration rate remained above 95 % during five repeated adsorption/desorption experiments, and the charging capacity was still about 96 % of the initial capacity even after 1000 CV cycles. Therefore, the NiFe LDH film could be a promising electroactive material for the removal of Cl− from aqueous solution.

Magnetoimpedance effect on multilayer [NiFe/Cu/NiFe]3 and supermultilayer [NiFe/Cu/NiFe]3/Cu/[NiFe/Cu/NiFe]3 on Cu PCB meander substrate

The effect of magneto-impedance on multilayer and super multilayer has been investigated. NiFe and Cu thin layer samples were prepared by electrodeposition method on a meander patterned Cu PCB substrate. The phenomenon of magneto-impedance ratio is measured using low frequencies (20 kHz-100 kHz). The magneto-impedance ratio increases as the number of frequencies increases. The results showed that the super multilayer structure has a larger magneto-impedance ratio than the multilayer structure.