Fundamental studies on graphene (Gr) and its real device applications have been affected by unavoidable defects and impurities which are usually present in synthesized Gr. Therefore, post treatment ...methods on Gr have been an important subject of research followed by the community. Here, we demonstrate a post-treatment of cm-sized CVD-grown graphene in a Radio Frequency-generated low-pressure plasma of methane and hydrogen to remove oxygen functional groups and heal the structural defects. The optimum plasma treatment parameters, such as pressure, plasma power, and the ratio of the gases, are optimized using in-situ optical emission spectroscopy. This way we present an optimal healing condition monitored with in situ OES. A twofold increase in the conductivity of plasma-treated Gr samples was obtained. Plasma treatment conditions give insights into the possible underlying mechanisms, and the method presents an effective way to obtain improved Gr quality.
Oscillation of physical parameters in materials can result in a peak signal in the frequency spectrum of the voltage measured from the materials. This spectrum and its amplitude/frequency tunability, ...through the application of bias voltage or current, can be used to perform neuron-like cognitive tasks. Magnetic materials, after achieving broad distribution for data storage applications in classical Von Neumann computer architectures, are under intense investigation for their neuromorphic computing capabilities. A recent successful demonstration regards magnetisation oscillation in magnetic thin films by spin transfer or spin orbit torques accompanied by magnetoresistance (MR) effect that can give a voltage peak in the frequency spectrum of voltage with bias current dependence of both peak frequency and amplitude. Here we use classical magnetoimpedance (MI) effect in a magnetic wire to produce such a peak and manipulate its frequency and amplitude by means of the bias voltage. We applied a noise signal to a magnetic wire with high magnetic permeability and owing to the frequency dependence of the magnetic permeability we got frequency dependent impedance with a peak at the maximum permeability. Frequency dependence of the MI effect results in different changes in the voltage amplitude at each frequency when a bias voltage is applied and therefore a shift in the peak position and amplitude can be obtained. The presented method and material provide optimal features in structural simplicity, low-frequency operation (tens of MHz-order) and high robustness at different environmental conditions. Our universal approach can be applied to any system with frequency dependent bias responses.
Aiming to enhance the performance of magnetic field sensors, this study focuses on depositing electrospun TiO
2
/PVA/CTAB composite nanofibers onto cobalt-based amorphous magnetic ribbons. The ...nanofibers have diameters of about 175–325 nm, where TiO
2
nanoparticles are uniformly dispersed in the fibers. The nanofiber-coated ribbons were analyzed using the giant magneto impedance (GMI) effect and we measured significant variation in the GMI ratio. The results demonstrate that the GMI response of the ribbon coated with nanofibers electrospun for 15 min exhibits a remarkable increase of 340% at a frequency of 10 MHz, compared to 290% for the uncoated ribbon. Nanofibers can be utilized for chemically or physically bonding additives to their surface, particularly for applications, where it is needed, for example, to detect biomaterials. Given their dielectric nature, these fibers hold potential for shielding against space charges and adhering to chemical components. They can be integrated with other materials to enhance the magnetoimpedance effect. Therefore, the application of non-magnetic electrospun nanofibers as coatings on magnetic sensors shows significant promise in augmenting their sensitivity and overall performance.
Abstract
We demonstrate a nanostructure layer made of Ni
80
Fe
20
(permalloy:Py) thin film conjugated MoS
2
nano-flakes. Layers are made based on a single-step co-deposition of Py and MoS
2
from a ...single solution where ionic Ni and Fe and MoS
2
flakes co-exist. Synthesized thin films with MoS
2
flakes show increasing coercivity and enhancement in magneto-optical Kerr effect. Ferromagnetic resonance linewidth as well as the damping parameter increaseed significantly compared to that of the Py layer due to the presence of MoS
2
. Raman spectroscopy and elemental mapping is used to show the quality of MoS
2
within the Py thin film. Our synthesis method promises new opportunities for electrochemical production of functional spintronic-based devices.
Abstract
The interfacial Dzyaloshinskii-Moriya Interaction (iDMI) is an antisymmetric exchange interaction that is induced by the broken inversion symmetry at the interface of, e.g., a ...ferromagnet/heavy metal. Thus, the presence of iDMI is not expected in symmetrical multilayer stacks of such structures. Here, we use thermal annealing to induce the iDMI in a Py/Pt
×10
symmetrical multilayer stack. Brillouin light scattering spectroscopy is used to directly evidence the iDMI induction in the annealed sample. Structural characterizations highlight the modified crystallinity as well as a higher surface roughness of the sample after annealing. First principles electronic structure calculations demonstrate a monotonic increase of the iDMI with the interfacial disorder due to the interdiffusion of atoms, depicting the possible origin of the induced iDMI. The presented method can be used to tune the iDMI strength in symmetric multilayers, which are the integral part of racetrack memories, magnonic devices as well as spin-orbitronic elements.
The aim of this study was to investigate the geometrical patterns seen on the surface of chemical vapor deposited (CVD) graphene using fractal analysis of surface topography images obtained from ...atomic force microscopy (AFM) and scanning electron microscopy (SEM) and refer them to the structural data derived using Raman spectroscopy. From this comparison, an insight into structural properties of prepared samples was possible, and performed analysis helped to obtain a comprehensive understanding of a role of physicochemical processes to the shaping of three-dimensional (3D) microtextured surfaces.
•The anisotropic magnetoresistance (AMR) in permalloy (NiFe, Py)/MoS2 bilayers is systematically studied.•A strong enhancement of AMR by the MoS2 layer is observed.•The AMR enhancement cannot be due ...to presence of the spin Hall magnetoresistance.•The enhanced AMR in the Py/MoS2 bilayers can be attributed to the interfacial hybridization at the interface.
The anisotropic magnetoresistance (AMR) in permalloy (NiFe, Py)/MoS2 bilayer is studied and a strong enhancement of AMR in Py layer is observed due to the MoS2 coating on its surface. The spin Hall magnetoresistance and the induced magnetic moment by interfacial magnetic proximity effect at the Py/MoS2 interface cannot explain the observed AMR enhancement. In order to find the origin of the observed MR increase in Py/MoS2 sample, the magnitude of magnetic anisotropy constants are derived from torque curves on the basis of AMR data. The enhanced AMR in the Py/MoS2 bilayers can be attributed to the interfacial hybridization at the interface. Our findings enrich the understanding of the magnetoresistance of metallic FM/transition metal dichalcogenide (TMDC) bilayers and present AMR enhancement for application in spintronic devices.
•Surface-charge engineering via near-field electrospinning enhances Magnetoimpedance (MI) response.•Interface alignment of fibers influences the ferroelectric/ferromagnetic interaction, impacting MI ...response.•The anisotropic TiO2/PVA/CTAB composite fibers generate single-peak MI patterns in Co-based ribbons.•NFES-produced surface charges underpin a potential avenue for magnetic material modification in flexible magnetoelectric devices.
Magnetoimpedance (MI) elements show potential application in detection devices as well as advanced electronic components such as neuro-morphing computing and magneto-ionics. We demonstrate surface-charge accumulation via the transformative impact of near-field electrospinning on MI response of Co-based ribbons via longitudinal or transverse formation of aligned TiO2/PVA/CTAB composite fibers. MI represents sensitivity changes against anisotropic charge accumulation designed at the surface via longitudinally or transversely grown fibers. Notably, MI for the longitudinal electrospun exhibits a unique single-peak pattern, in contrast to the conventional dual-peak behavior. This variation is attributed to the meticulous alignment of fibers along the length and width of the ribbons, triggering a dynamic interplay at the crucial ferroelectric/ferromagnetic interface. Our finding demonstrates MI response control through interacting with anisotropic-order of surface-charge mediated by composite fibers.
Redox reactions at the metal/electrolyte interface are the basis of electrochemical metallization memristors that can be understood through cyclic voltammetry (CV). However, voltage limitation during ...the CV measurements that prevents the resistance switching has limited full understanding of the redox reactions. We apply a thickened ≈20 μm graphene oxide (GO) electrolyte layer in a memristor structure and show that all redox reactions can be determined through CV measurements without resistance switching by sweeping the voltage up to high values. We are able to unhide details of Ag redox reactions (Agz+/Ag) utilizing a GO thick layer as the solid electrolyte in Pt/GO/Ag cell structure. The results are fundamentally valuable for designing methods to uncover the memristive mechanisms of memristors.
The low thickness of solid electrolytes in memristors hinders usage of the cyclic voltammetry study method of them due to fast switching of the resistance. The authors suggest using a thick layer to overcome this problem.
High performance, low density and easy preparation are desirable attributes of electromagnetic wave absorption materials. In this study, we prepared graphene flakes containing ellipsoid like magnetic ...Ni, Fe and NiFe-nano-particles in a one-step electrochemical deposition process. The synthesized nanoparticles presenting a superparamagnetic-like response. The saturation magnetization of the Gr/Ni, Gr/Fe, and Gr/NiFe hybrid nanocomposites was 4.4, 371.7, and 546.8 kA/m, respectively, and a coercivity of 1454, 3500, and 2000 A/m, respectively. The total Electromagnetic shielding of these fabricated composites reached 25, 20, and 18.5 dB, in the X band. In the Gr/NiFe nano-composites, the improvement in microwave screening is due to high saturation magnetization and small coercivity of magnetic filler, and higher ac conductivity.
Display omitted
•Preparation graphene flakes containing ellipsoids like magnetic Ni, Fe, and NiFe-nano-particles in a one-step electrochemical deposition process.•Considering to the percolation threshold of the synthesized nanoparticles in preparing the electromagnetic absorber to avoid the reflection of the waves.•Electromagnetic shielding capability of the embedded Fe and Ni-nanoparticles structures via trapping of the waves via multiple internal scattering.•The enhanced nanocomposite with great potential applications as a microwave absorber in hiding technology.
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