Weyl semimetal Td‐phase WTe2 possesses the spin‐resolved band structure with strong spin–orbit coupling, holding promises as a useful spin source material. The noncentrosymmetric crystalline ...structure of Td‐WTe2 endows the generation of the out‐of‐plane polarized spin, which is of great interest in magnetic memory applications. Previously, WTe2 was explored in spin devices based on mechanically exfoliated single crystal flakes with a size of micrometers. For practical spintronics applications, it is highly desirable to implement wafer‐scale thin films. In this work, centimeter‐scale chemical vapor deposition (CVD) grown Td‐WTe2 thin films are used and the spin current generation is studied by the spin torque ferromagnetic resonance (ST‐FMR) technique. The in‐plane and out‐of‐plane spin conductivities of 7.36 × 103 (ℏ/2e) (Ωm)–1 and 1.76 × 103 (ℏ/2e) (Ωm)–1, respectively, are found in CVD‐growth 5 nm‐WTe2. The current‐induced magnetization switching in WTe2/NiFe is demonstrated at room temperature in the domain wall motion regime, which may invigorate potential spintronic device innovations based on Weyl semimetals.
Weyl semimetal WTe2 holds promise as a useful spin current generator, which was previously explored in mechanically exfoliated flakes. Here, centimeter‐scale chemical vapor deposition WTe2 thin films are used and both the in‐pane and out‐of‐plane spin currents are found. The results are highly desirable for practical applications and provide an impetus for magnetization switching devices using Weyl semimetals.
This study has been motivated by cancer research, in which heterogeneity analysis plays an important role and can be roughly classified as unsupervised or supervised. In supervised heterogeneity ...analysis, the finite mixture of regression (FMR) technique is used extensively, under which the covariates affect the response differently in subgroups. High-dimensional molecular and, very recently, histopathological imaging features have been analyzed separately and shown to be effective for heterogeneity analysis. For simpler analysis, they have been shown to contain overlapping, but also independent information. In this article, our goal is to conduct the first and more effective FMR-based cancer heterogeneity analysis by integrating high-dimensional molecular and histopathological imaging features. A penalization approach is developed to regularize estimation, select relevant variables, and, equally importantly, promote the identification of independent information. Consistency properties are rigorously established. An effective computational algorithm is developed. A simulation and an analysis of The Cancer Genome Atlas (TCGA) lung cancer data demonstrate the practical effectiveness of the proposed approach. Overall, this study provides a practical and useful new way of conducting supervised cancer heterogeneity analysis.
Magnons and plasmons are different collective modes, involving the spin and charge degrees of freedom, respectively. Formation of hybrid plasmon–magnon polaritons in heterostructures of plasmonic and ...magnetic systems faces two challenges, the small interaction of the electromagnetic field of the plasmon with the spins, and the energy mismatch, as in most systems plasmons have energies orders of magnitude larger than those of magnons. We show that graphene plasmons form polaritons with the magnons of two-dimensional ferromagnetic insulators, placed up to to half a micrometer apart, with Rabi splittings in the range of 100 GHz (dramatically larger than cavity magnonics). This is facilitated both by the small energy of graphene plasmons and the cooperative super-radiant nature of the plasmon–magnon coupling afforded by phase matching. We show that the coupling can be modulated both electrically and mechanically, and we propose a ferromagnetic resonance experiment implemented with a two-dimensional ferromagnet driven by graphene plasmons.
Microstrip line ferromagnetic resonance (MS-FMR) has been used to investigate the dependence of the magnetic damping enhancement on the thickness of Co20Fe60B20 and Pt due to spin pumping. Samples ...with variable thicknesses of Co20Fe60B20 (Pt) are used to determine the spin mixing conductance (spin diffusion length) via the thickness dependence of the Gilbert damping parameter α of Co20Fe60B20/Pt heterostructures. The results obtained from the analysis of the MS-FMR measurements reveal that α increases linearly with the inverse thickness of Co20Fe60B20 for films capped with a 10 nm thick Pt layer, while the variation of α versus the Pt thickness of the 4 nm thick Co20Fe60B20 layer has an exponential behaviour. The experimental data was analysed using a ballistic or a diffusive spin transport model for spin pumping, which includes the effective spin mixing conductance of the CoFeB/Pt interface and the spin-diffusion length of Pt. The estimated values are 37.5 nm−2 (spin mixing conductance) and 1.7 nm when the ballistic transport model is used, and 56.75 nm−2 and 2.2 nm when the experimental data are analysed using a more realistic model based on a diffusive transport. Moreover, MS-FMR measurements reveal that the effective magnetization varies linearly with the Co20Fe60B20 inverse thickness due to the perpendicular interface anisotropy. This anisotropy, estimated to be 1.31 erg cm−2, reinforces the perpendicular magnetization easy axis.
•Strong increase in the relaxation rate was investigated at temperatures below 100 K in epitaxial iron garnet films.•Compound with Gd3+ ions is formed in the transition layer, which has a ...considerable magnetic moment.•Unlike other relaxation mechanisms, this one cannot be compensated for.•For further improvement we suggest to use substrates without strong paramagnetic ions like a Y3Ga3Sc2O12 substrate.
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We have investigated the intermediate layer between the gallium-gadolinium garnet substrate and the yttrium-iron garnet epitaxial film. This interlayer is characterized by a large magnetic moment at low temperatures, which leads to an anomalous dependence of the susceptibility and a shift in the magnetic resonance frequency upon cooling. This shift is much larger than might be expected due to magnetization anisotropy, substrate paramagnetic ions, and magnetostriction. We found that this interlayer plays a major role in magnetic relaxation processes in the temperature range below 50 K.
25nm to 50nm Co2FeAl (CFA) thick wire arrays with varying widths and spacing have been patterned from continuous CFA films deposited on MgO(001) using e-beam lithography and Ar ion milling. ...Magneto-optical Kerr effect, transverse bias initial inverse susceptibility and torque measurements reveal that the in-plane magnetic anisotropy of the wires is dominantly monitored by a uniaxial term, in contrast with the continuous films where it is governed by the superposition of a fourfold term and of a smaller uniaxial term. The microstrip ferromagnetic resonance spectra performed using a magnetic field H, applied in the plane of the studied sample along various directions, or perpendicularly to this plane, gave us access to various quantized modes originating from the patterning. In addition, Brillouin light scattering also exhibits quantized modes. A large part of the experimental observations can be quantitatively interpreted as resulting from the demagnetizing terms induced by the geometrical patterning. However, the presented model, simply built on the effect of the demagnetizing field, is not able to give account of all the quantized modes present in the resonance spectra. When H is parallel to the wires, a more complete description is used: it considers the wave-vector quantization induced by the patterning. For the magnetic modes concerned by both approaches, the correspondence between the 2 models is easily established. When H is not parallel to the wires quantitative descriptions of the behavior of the field dependence of the observed modes still can often be performed. Finally, in all the studied patterned samples, the uniform magnetic mode, termed “film mode”, relative to the parent continuous film is observed by ferromagnetic resonance: such a behavior, which has been reported previously, remains to be completely interpreted.
•The static and dynamic properties of Co2FeAl wire arrays have been studied.•Microstrip ferromagnetic resonance reveals the presence of several spin wave modes.•Some modes result from the magnetic wave confinement due to the finite wire width.•The mode quantization is confirmed by the Brillouin light scattering observations.•The experimental results can be interpreted as resulting from the demagnetizing term.
Interfaces of ferromagnetic transition metals such as Iron, Cobalt, and Nickel with non-magnetic palladium are of interest due to their unique magnetic and spintronic properties. These interfaces ...enable ferromagnetic resonance (FMR) based sensing of hydrogen gas. In the present work, we synthesized Fe3O4–Pd core-shell nanospheres via a one-pot synthesis method using the thermal decomposition of Fe3+ acetylacetonate in the presence of a reducing agent to produce the Fe3O4 core, followed by the reduction of a Pd2+ precursor to form the pure Pd shell. We found that our in-situ synthesized core-shell nanostructure is magnetically active and shows excellent H2 gas sensing properties. The effect of reversible hydrogen gas absorption on the magnetism of Fe3O4–Pd core-shell nanospheres was investigated. The hydrogen-induced ferromagnetic-resonance (FMR) peak shift amounted to 30% of the peak linewidth for the virgin state of the sample. In addition, in the presence of hydrogen gas, we observed a fully reversible decrease in the FMR peak linewidth by about two times. This was accompanied by a nearly doubling of the FMR peak height. Response and recovery times of about 2 and 50 s, respectively, were extracted from the measurements. All the data was collected using a mix of just 3% hydrogen in a nitrogen carrier gas.
•FeO–Pd core-shell nanospheres for the efficient detection of hydrogen gas were employed.•A one-pot synthesis method was developed to produce FeO–Pd core-shell nanospheres.•The core-shell nanosphere system showed a fast response and recovery times.•The nanospheres demonstrated superior FMR signal and reversible change upon hydrogenation.
Four novel D-π-A extended styryl colorants containing carbazole unit were designed and modified synthetically to evaluate the effect of various acceptors on ICT (intramolecular charge transfer) ...characteristics and to investigate the effect of incorporation of an additional π-bond along with the assistance of electron withdrawing chlorine group in the conjugation. Dye 4d with rhodanine-3-acetic acid and 4c with 2-(benzothiazol-2-yl) cyanomethylene showed the longer absorption and emission maxima than 4a and 4b in the polar solvents. The studied dyes exhibited positive solvatochromism and large Stokes shift due to twisted geometry. ICT characteristics of dyes were confirmed with the help of different solvent polarity plots to afford the validation of ICT character. The order of εmax (molar absorption coefficient) was found as, 4c > 4d > 4b > 4a. All the studied dyes demonstrated good fluorescence molecular rotor (FMR) properties. Dyes 4c and 4d showed better sensitivity towards the viscosity with x = 0.33 and x = 0.30 respectively. The experimental and the computational studies were opted to study the NLO (Non-linear optical) characters of the dyes. Smallest band gap in 4c and 4d amongst all the four dyes was evident from the higher values of “linear polarizability (α0)”, “first order hyperpolarizability (β) “and “second order hyperpolarizability (γ)”. These dyes have showed better NLO properties than urea. DFT calculations (B3LYP/6-31 + G(d) and CAM-B3LYP/6-31 + G(d) were employed to understand the structural and electronic behaviour of 4a-4d which also have supported the experimental results. Thus, from the observed results of the solvatochromic and computational method, reported new carbazole styryls were found to be a good candidate of FMR and NLO material.
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•The influence of the type of deposition solution and pH is presented for nickel nanowires.•The influence of pH is evident as it alters the deposition rate if we use pH of 2.5 and 3.5.•The FMR ...resonance field values showed evidence of structural changes within the wires.
This study presents the influence of pH and precursors present in the electrolyte on the microstructure and magnetic properties of nickel nanowires. Polycarbonate membranes were used as a template for electrodeposition of nanowires. The SEM results showed that the wires have lengths ranging from 2.68 ± 0.28 µm to 18.77 ± 1.18 µm. X-ray diffraction confirmed the fcc structure of Ni0 and demonstrated how different solutions can modify the reflection intensity of the peaks. Finally, ferromagnetic resonance spectra demonstrated how pH and precursors present in the electrolyte can modify the ferromagnetic response of NiNWs grown on polycarbonate membranes, emphasizing the influence of both factors on the magnetic behavior of nanowires. This study provides an understanding of the role that solution chemistry plays in the manufacture of magnetic nanomaterials.
Due to its excellent magnetic properties, MgZn ferrite is a nearly optimal material for low temperature co-fired ceramic (LTCC) phase shifter applications. In this study, low temperature co-fired ...Mg0.8Zn0.2-xCdxFe2O4 ferrites (x = 0.00–0.10, with increments of 0.02) were synthesized using a solid-state method with the aid of 2.5 wt% BBSZ (33%mol Bi2O3-21%mol B2O3-11%mol ZnO-35%mol SiO2) glass sintering. The effects of the Cd2+ ions on phase formation, microstructure, magnetic permeability, and gyromagnetic properties were investigated. The results indicated that a suitable amount of Cd2+ ion substitution did not change the phase formation of MgZn ferrite. However, with further increases of the Cd2+ ion content, the superfluous Cd2+ ions and Fe3+ ions formed CdFe2O4, which affected the microstructure, density and magnetic properties of the samples. More specifically, when x = 0.04, Mg0.8Zn0.16Cd0.04Fe2O4 ferrite, sintered at 920 °C, showed excellent magnetic permeability (μ'~56.6 @1 MHz–20 MHz) and had a high cut-off frequency (~100 MHz). Furthermore, the ferromagnetic resonance line widths (ΔH) were measured as a function of the Cd2+ substitution at 9.56 GHz, and the relationships between ion occupancy and microstructure were also discussed. A narrow ΔH (~228.2 Oe) can be obtained by adding an optimal amount of Cd2+ ions. These observations indicate that MgZn ferrites with a suitable amount of Cd2+ ions are promising candidate materials for LTCC electronic device applications.
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