Zhenjie Zhao

Enhancement of giant magnetoimpedance effect of electroplated NiFe/Cu composite wires by dc Joule annealing

The influence of dc Joule annealing of electroplated Ni80Fe20/Cu composite wires on their giant magnetoimpedance (GMI) effect is presented in this article. Successive thermal treatments by dc Joule annealing with the current density ranging from 2.4 to 9.6×108 A/m2 were applied to the composite wires for a fixed annealing time of 1 min to release the residual stresses in the plated NiFe layer. The results showed that the magnetoimpedance (MI) effect of the composite wires can be greatly enhanced by dc Joule annealing. For electroplated 1.5 μm of the Ni80Fe20 layer on a copper wire of 20 μm diameter, the optimum annealing current density was found to be 7.2×108 A/m2 and from such annealing the MI ratio was increased from 637% to 1110%, a 74% increment. The optimum ac driving frequency for the GMI effect of the annealed wires under the influence of the annealing conditions in relation to the skin effect and permeability variation in the wires was investigated and discussed. The optimum procedure of dc Joule...

Effect of magnetic field on the magnetic properties of electroplated NiFe/Cu composite wires

The effect of the magnetic field on the magnetic properties of NiFe/Cu composite wires electroplated under a longitudinal magnetic controlling field is presented. Composite wire samples of 20-μm-diameter Cu electroplated with a layer of Permalloy™ (Ni80Fe20) under the influence of a longitudinal magnetic field of intensities ranging from 0 to 400 Oe were produced, and the microstructure and magnetic properties were measured. The results showed that the longitudinal magnetic field in the composite wire plating makes the packing of the crystals in the plated layer more orderly, and thus increases the uniformity and magnetic softness of the plated material. It also shifts the magnetic anisotropy of the plated layer from circumferential to longitudinal, and increases the critical frequency of the plated composite wire in magnetoimpedance effect testing, at which the magnetoimpedance ratio reaches the maximum.

Development of high permeability nanocrystalline permalloy by electrodeposition

In this study, for developing microsensors for weak magnetic field, methods for developing high permeability nanocrystalline permalloy by electrodeposition and the relationship between the grain size and magnetic properties of the nanocrystalline permalloy are investigated. By dc plating with and without saccharin added and pulse plating with saccharin added, permalloy samples of grain sizes from 52 nm to 11 nm are obtained. The coercivity and magnetoimpedance (MI) ratio of the samples are tested against the grain size variation. Results show that the coercivity decreases rapidly and MI ratio increases greatly with grain size decrease from 52 nm to 11 nm.

One-step hydrothermal synthesis of Fe3O4@C nanoparticles with great performance in biomedicine

Core-shell structured Fe3O4@C nanoparticles were fabricated by a facile one-pot hydrothermal route. The structure and component of the nanoparticles were fully characterized by transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, Raman spectroscopy, thermogravimetric analysis, magnetometry and Brunauer-Emmett-Teller specific surface area measurements. The obtained Fe3O4@C nanoparticles possessed favorable dispersibility, high saturation magnetization (61.4 emu g-1) that could quickly respond to external magnetic field and excellent biocompatibility. Excitingly, the experiments of the Fe3O4@C nanoparticles as drug carriers revealed an efficient drug-loading as high as 1.08 mg mg-1. More importantly, the drug loading composite exhibited pH-responsive release profiles and the duration was as long as 200 h; at the pH value of 5.8 and 7.4, the release rate was 93.7% and 33.6%, respectively. Furthermore, the obtained Fe3O4@C nanoparticles had good magneto-thermal ability. All these positive attributes make the as-prepared Fe3O4@C nanoparticles a promising platform for further biomedical evaluations.

Giant magnetoimpedance effect in CuBe/NiFeB and CuBe/insulator/NiFeB electroless-deposited composite wires

The giant magnetoimpedance (GMI) effect of CuBe/NiFeB and CuBe/insulator/NiFeB composite wires prepared by electroless-deposition was investigated. The results showed that geometry dimension has a significant influence on the GMI effect of CuBe/NiFeB composite wire. As the NiFeB layer thickness approaches the skin depth of the NiFeB layer, maximum GMI will be expected; it reaches -23% at 1 MHz. After adding an insulator layer, the GMI ratios of CuBe/insulator/NiFeB composite wire were much higher than those of CuBe/NiFeB composite wire. The maximum GMI ratio of CuBe/insulator/NiFeB composite wire was 250% at 500 kHz-1 MHz. This result is related to current redistribution under the external magnetic field and the electromagnetic interaction between the conductive core and the ferromagnetic layer, and also is related to the skin effect and eddy current of the sample.

First-principles investigation of the effect of pressure on BaFe 2 As 2

On the experimental side,

The GMI effect in nanocrystalline FeCuNbSiB multilayered films with a SiO2 outer layer

{\text{BaFe}}_{2}{\text{As}}_{2}

X-ray diffraction and Mössbauer studies of γ'-(Fe1-xSnx)4N compounds (0.0≤x≤0.3)

without doping has been made superconducting by applying appropriate pressure (2--6 GPa). Here, we use a full-potential linearized augmented plane-wave method within the density-functional theory to investigate the effect of pressure on its crystal structure, magnetic order, and electronic structure. Our calculations show that the striped antiferromagnetic order observed in experiment is stable against pressure up to 13 GPa. Calculated antiferromagnetic lattice parameters are in good agreements with experimental data, while calculations with nonmagnetic state underestimate Fe-As bond length and

A facile, green synthesis of highly fluorescent carbon nanoparticles from oatmeal for cell imaging

c

Longitudinally driven magneto-impedance effect in annealed Fe-based nanocrystalline powder materials

-axis lattice constant. The effects of pressure on crystal structure and electronic structure are investigated for both the antiferromagnetic state and the nonmagnetic one. We find that the compressibility of the antiferromagnetic state is quite isotropic up to about 6.4 GPa. With increasing pressure, the