Zhen Wang

Chang'an University · Department of Applied Physics

Spin–orbit torque (SOT) can provide efficient electrical manipulation of magnetism via applying electrical current to breaking the symmetry of damping-like torque. In the heterojunction of heavy and ferromagnetic metal, Dzyaloshinskii–Moriya interaction (DMI) is one of the key ingredients for stabilizing chiral spin structures, like chiral domain w...

The crystalline mechanism of the Pt50Au50 alloy with grain boundary (GB) segregation during the rapid solidification process is investigated using molecular dynamics simulations. The cluster evolution and phase transformation processes during the GB segregation are analyzed by means of the energy temperature (E-T) curve, the pair distribution funct...

Interfacial polarization is generally a major cause of dielectric loss, but its exact contribution to the electromagnetic wave (EMW) absorption capacity of absorbers remains to be elucidated. In this work, SnO2@rGO composite (S2) with tight interfaces formed by chemical bonds and SnO2/rGO mixture (S3) were synthesized by a simple chemical route fol...

Controlling defects and interfaces in composite absorbers can effectively regulate electromagnetic (EM) parameters and enhance the electromagnetic wave (EMW) absorption ability, but the mechanism still needs to be further elucidated. In this study, ZnFe2O4/ZnO/C composite was synthesized via the hydrothermal method followed by post-annealing in dif...

ZnO has broad application prospects in the field of LED lighting and display. However, the unclear luminescence mechanism limits the improvement of luminous efficiency and the realization of controllable luminescence. Herein, intrinsic defects (Zni and VO) in sol-gel ZnO thin films were controlled by post-annealed in different atmospheres (air, N2...

Al³⁺ and Nb⁵⁺ co-doped rutile TiO2 ceramic samples were prepared by solid state reaction. Raman spectra, element mapping and EDX confirmed that (Al + Nb) dissolved into grain. The samples showed colossal permittivity (ε′≈3.8 × 10⁴) with low dielectric loss (under 0.08) over frequency (20 Hz–100 kHz) and temperature (80 K–240 K) ranges. Abnormal mul...

This study investigates the magnetic dynamics of a ferroelectric/ferromagnetic heterostructure mediated by a charge/strain-induced magnetoelectric interaction that exhibits a pronounced dynamic magnetic response to an electric field. In the experimental process, the epitaxial strain gave rise to electrically tunable uniaxial magnetic anisotropy, an...

FeGa/FeNi bilayer structures with different deposition order were fabricated by the electrodeposition method on indium tin oxide (ITO) substrates. The structure, morphology, static and dynamic magnetic properties of FeGa/FeNi (FeNi/FeGa) films were investigated. The bilayer structures exhibit extremely various magnetic properties with different dep...

The deformation behaviour of Au twinned nanowire is investigated by molecular dynamic simulation. It is found that the relationship of yield strength with twin boundary spacing (TBS) can be divided into three ranges. The deformation mechanism of Au twinned nanowire is revealed according to the dislocation–twin interactions. For those with large and...

The mechanical behaviour of rapidly solidified aluminium with multiple twinned nanograins is investigated by a large-scale molecular dynamics simulation. The nanocrystalline structures with mean grain sizes ranging from 3.1 nm to 24.4 nm are prepared by quenching liquid at appropriate cooling rates. It is found that the mechanical properties of rap...

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, t...

A thermal evaporation method in high vacuum has been developed to synthesize NPB nanostructures. The morphology, structure and cycle-testing of field emission behavior have been investigated. The field emission characteristics exhibit low turn-on field 6.25, 7.5 and 6.2 V/μm and maximum current density can reach 1.65, 2.4 and 2.0 mA/cm² for nominal...

Co/NM (nonmagnetic Ag and SiO2)/Co sandwich structure films with different thicknesses of NM were fabricated on Si(111) substrate via oblique radio frequency sputtering. With increasing thickness of nonmagnetic Ag (tAg), in-plane magnetic anisotropy field Hk initially increased from 100 Oe of tAg = 0 nm to 220 Oe of tAg = 1.5 nm, and then decreased...

Spin-dependent transport properties of Fe3O4 spheres with diameters from 200 nm to 900 nm have been investigated and polyethylene glycol (PEG) exists on the surface of Fe3O4 particles. The nonlinear I-V curve became obvious with the increase of Fe3O4 diameter, which indicated the tunneling barrier height decreases with the increasing diameter. The...

The effect of the cooling rate on the solidification process of liquid aluminium is studied using a large-scale molecular dynamics method. It is found that there are various types of short-range order (SRO) structures in the liquid, among which the icosahedral (ICO)-like structures are dominant. These SRO structures are in dynamic fluctuation and t...

In a bilayer system of Bepp2-FeCo, the element content variation and chemical states of the Bepp2-FeCo interface were investigated using X-ray and ultraviolet photoelectron spectroscopy with Ar ion etching. Chemical reaction was observed for Co and Fe with Bepp2 at the interface. Ultraviolet photoelectron spectroscopy results showed a large downwar...

Self-assembled flowerlike α-Fe2O3, Fe3O4 and γ-Fe2O3 were fabricated by a simple calcination procedure. The structure characterization shows that the flowerlike morphology and the size of the nanostructures are perfectly maintained in the conversion of precursor to α-Fe2O3, Fe3O4, and γ-Fe2O3. The complex permittivity and permeability results indic...

Two kinds of novel blue-emitting materials, anthracene-based derivatives, are synthesized by the Suzuki coupling reaction. It is worth noting that the maximum emission wavelengths of the two materials are 441 and 444 nm in tetrahydrofuran and 456 and 454 nm in film states, which are the typical blue fluorescence and the fluorescence quantum yields...

The interface between the organic and magnetic electrodes is a fundamental problem in organic spintronics devices. Therefore, bilayer structure of Alq3/FeCo was fabricated in a dual ultra high vacuum chamber. The electronic structure of Alq3–FeCo interface has been studied by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectrosco...

FeCo films with various thicknesses were fabricated by direct-current magnetron sputtering on corning glass and organic ferroelectric PVDF substrates at the same time with 5 nm Ru seed layer and 5 nm Ta protective layer. The in-plane uniaxial anisotropy field of FeCo on glass substrate increases from 24 to 36 Oe with the increase of FeCo film thick...

The interface has become an important issue in organic magnetic spin-valves. In this work, Si/FeCo/Ta, Si/FeCo/Bepp2/Ta, and Si/Bepp2/FeCo/Ta samples with the variation of the FeCo layer thickness were fabricated by direct-current magnetron sputtering for FeCo layers and the thermal evaporation method for Bepp2 layers. The interaction at the interf...

Strip-like FeCo films were patterned by a traditional lithograph process from intrinsically isotropic continuous FeCo films. The strip-patterned FeCo film shows a strong in-plane uniaxial magnetic anisotropy with easy axis along the length direction of the strip. The angular dependences of remanence ratio, switching field, and coercivity indicate t...

Co2FexMn1−xSi (0 x 1) Heusler alloys were fabricated by arc-melting the stoichiometric quantities of the constituents. We investigated the magnetic properties, geometric structure simulation, and real crystal structure for powder samples and the magnetic damping constant for polished thin-disk samples. All samples show high Curie temperatures, and...

The CrO2 micro rod powder was synthesized by decomposing the CrO3 flakes at a specific temperature to yield precursor and annealing such a precursor in a sealed glass tube. The magneto-transport properties have been measured by a direct current four-probe method using a Cu/CrO2 rods/colloidal silver liquid electrode sandwich device. The largest mag...

An electric-field pulses driven magnetoelectric memory cell in a single layered ferromagnetic thin film was fabricated by direct-current magnetron sputtering Ru/Fe65Co35 on ferroelectric (110) [Pb(Mg1/2 Nb2/3)O3]0.68-[PbTiO3]0.32 (PMN-PT) substrates. The magnetization in the orthogonal directions can be reset by the positive/negative electric field...

Magnetic damping constant (alpha) is one of the key parameters to determine the critical current density of spin-transfer-torque devices and the switching time of magnetization for ultra-high-frequency devices. In this work, Gd doped FeCo films were fabricated to investigate alpha based on the ferromagnetic resonance technique. Gd doping not only c...

The field emission (FE) properties of vertically aligned carbon nanotube (CNT) arrays having a surface decorated with Ta layer were investigated. The CNTs with 6 nm thickness of Ta decoration showed improved FE properties with a low turn-on field of 0.64 V/μm at 10 μA/cm2, a threshold field of 1.06 V/μm at 1 mA/cm2 and a maximum current density of...

FeCoSi magnetic thin film with in-plane uniaxial anisotropy was fabricated on glass substrate by RF magnetron co-sputtering. A FeCoSi/PZT actuator heterojunction was obtained through a parallel bonding with magnetic film's original easy-magnitization axis along the PZT actuator's length direction, which is the main direction for stress generating,...

Large electric field tunable remanent magnetization and in-plane anisotropy in a Fe65Co35 film was observed in sputtered ferromagnetic/ferroelectric heterostructures. Two stable magnetization directions were established through a 90° transition of the in-plane uniaxial anisotropy of FeCo film under a positive electric field, and large nonvolatile r...

The magnetic FeCoGd thin films with various sputtering power from 10 to 30 W were fabricated on glass substrates by magnetron co-sputtering. The crystal structure of as-deposited FeCoGd thin films was investigated by X-ray diffraction. And an increasing trend of grain size with the increasing sputtering power was shown. When sputtering power is bel...

Gd doped magnetic FeCo thin films were fabricated by DC magnetron co-sputtering at ambient condition. The structure transition from nano-crystalline structure to crystalline structure were characterized by XRD upon increasing sputtering power. A spin reorientation transition from in-plane uniaxial anisotropy to perpendicular anisotropy was observed...

FeTa films with thickness of 110 nm are fabricated on glass substrates by magnetron sputtering, and then a series of strips is designed on the FeTa films by conventional optical lithography and the ion beam etching method. Patterned FeTa strips show a tunable in-plane uniaxial magnetic anisotropy property in contrast with the magnetic isotropic pro...

Amorphous tris-(8-hydroxyquinoline)aluminum (Alq3) layers, which first form Alq3 islands and then grow into submicrometre thorns, with different nominal thicknesses are investigated. The field emission characteristics of Alq3 submicrometre thorns with nominal thicknesses of 20 nm, 50 nm and 100 nm include low turn-on fields of 3.2 V µm-1, 6.8 V µm-...

Ni-coated carbon nanotubes (CNTs) were synthesized by a simple chemical method. The multiresonance behavior in the permeability spectra was analyzed by the Gilbert modification of Landau–Lifshitz equation, indicating that the magnetic loss results from the magnetic exchange resonance more than the nature resonance. The sample shows a better electro...

The field emission behavior of aligned carbon nanotubes (CNTs) is remarkably improved by decorating their surfaces with Ti nanoparticles through a sputtering process. The CNT/Ti(4 nm) sample shows a low turn-on field of 0.63 V/lm at 10 mu A/cm(2), low threshold field of 1.06 V/mu m at 1 mA/cm(2), and maximum field emission current density of 23 mA/...

Co2FeAl nanoparticles were synthesized by reducing the coprecipitated precursor of CoCl2·6H2O, Fe(NO3)3·9H2O and Al2(SO4)3·18H2O under H2 atmosphere with various annealing temperatures and durations. X-ray diffraction and transmission electron microscopy were used to characterize the crystal structure and microstructure of Co2FeAl particles, respec...

Amorphous Fe nanoparticles and a nanonecklace were synthesized at room temperature by an aqueous reduction procedure, which provided a simple and potential method for volume production of ferromagnetic materials. The morphology was examined by scanning electron microscopy and transmission electron microscopy. The amorphism of Fe nanoparticles and t...

Spin-dependent transport property through molecules is investigated using a monolayer of oleic acid molecule self-assembled half metallic La0.7Sr0.3MnO3 (LSMO) nanoparticles, which was synthesized using a coprecipitation method. Fourier transform infrared spectroscopy was used to confirm that one-monolayer oleic acid molecules chemically bond to th...

FeNi thin films with the in-plane uniaxial anisotropy were fabricated by direct current magnetron sputtering. An FeNi/piezoelectric actuator hybrid structure was used to investigate the voltage-controlled magnetization switching. A theoretical calculation was performed to provide a simplified vision of the magnetoelastic contribution to the magneti...

A series of (Fe0.67Co0.33)1 − xSmx (0 ≤ x < 0.25) thin films with thickness around 110 nm have been fabricated on silicon(111) substrates by magnetron co-sputtering at ambient condition with a 2.4 kA/m magnetic field applied in the film plane during deposition. With the Sm concentration increasing, FeCo grain size gradually decreases and FeCoSm fil...

FeCoNd thin film with thickness of 166nm has been fabricated on silicon (111) substrates by magnetron co-sputtering and annealed for one hour under magnetic field at different temperatures (Ta) from 200°C to 700°C. The As-deposited and annealed FeCoNd film samples at Ta≤500°C were amorphous while the ones obtained at Ta≥600°C were crystallized. We...

The magnetic properties of FeNiSm thin films with different thicknesses, different Ta interlayer thicknesses and different numbers of Ta interlayers were investigated. The single layer FeNiSm shows in-plane uniaxial anisotropy at a thickness below critical value, but shows weak perpendicular anisotropy with a stripe domain structure at thickness ab...

The microwave absorption properties of nanosized double perovskite Sr2FeMoO6 and epoxy resin composites were investigated in the frequency range of 2–18GHz using the coaxial method. The Sr2FeMoO6 composites with an optimal 20wt% epoxy resin showed a strong electromagnetic attenuation of −49.3dB at 8.58GHz with a matching thickness of 2.15mm. Moreov...

CoFe2O4 nanoparticles were fabricated by a sol–gel method and then were coated with Co3Fe7–Co by means of a simple reduction process at different temperatures under 2% H2 with the protection of argon to generate the dielectric-core/metallic-shell structure. The optimum reflection loss (RL) calculated from permittivity and permeability of the 80 wt%...