Ru Bai

Output Characteristics of Two-Dimensional Spin Valve Chip

This paper investigated the output characteristics of a two-dimensional spin valve chip. The chip was placed in a series of rotating magnetic fields. The output relation curve of the two-dimensional spin valve chip transformed from a circle-like shape to a diamond-like shape with increasing magnetic field intensity because of the influence of the field perpendicular to the sensing axis. The experimental results fitted well with the simulation results. The output characteristics of the two-dimensional spin valve chip can be used to measure the direction of the magnetic fields.

Fabrication and Analysis of PM-biased Spin-valve Sensors

GMR spin-valve sensors are fabricated and analyzed, where a pair of CoPt permanent magnets (PM) are attached to two ends of the sensor elements to suppress the hysteresis. The size dependence of the spin-valve sensors is investigated by measuring GMR spin-valve sensing elements patterned with different lengths and widths. The results show that the GMR ratio reduces and the saturation field increases respectively with decreased length of the spin-valve sensor. And the saturation field also decreases with increasing width due to a stronger demagnetization effect. The experimental results are in good agreement with the theoretical prediction.

The Linewidth Dependence of GMR Properties in Patterned Spin Valve Resistors

The spin-valve structures with the configuration of NiFeCo(42.5A)/CoFe(15A)/ Cu(25A)/CoFe(42.5A)/CrPtMn(300A) were fabricated by RF diode sputtering. After a annealing process, the sheet spin-valve thin films were photolithographically patterned into serpentine resistors with different linewidths. The effect of linewidths on the magnetic properties and GMR ratio of patterned spin-valve resistors were studied. It was found GMR decrease with decreasing linewidths due to size effect and the effective anisotropy field Hk and the bias field field Hb are both inversely proportional to linewidths.

Fabrication of Various ZnO Nanostructures and their Photoelectric Properties

Various morphologies of ZnO nanostructures, including nanoparticle (NP), nanopetal and nanorod (NR) array, were fabricated via solution-phase approaches. The morphology and crystallization of resulting Nano-ZnO were investigated by Field-emission scanning electron microscope (FESEM), High resolution-transmission electronic microscope (HR-TEM), and X-ray diffraction (XRD), respectively. A dual-layered photoreceptor containing the nanostructures film as the charge generation layer (CGL) were designed and fabricated. It was found that the photoreceptor based on ZnO NR array as CGL exhibited better photoelectric performance than that from ZnO NP or nanopetal.

Effect of Buffer Layers on the Properties of NiFe/Cu/NiFe Trilayers

The properties of NiFe/Cu/NiFe trilayers with different buffer and cap layers are investigated. It is found that the properties of the NiFe/Cu/NiFe trilayers with a 50 Å NiFeCr buffer layer and a 50 Å NiFeCr cap layer exhibit a triangle transfer curve with a negligible hysteresis, showing a Giant magnetoresistance (GMR) ratio of 5.4%, and a saturation field of 272 Oe. In comparison, the trilayer deposited on a 50 Å Cu exhibits no GMR effect. It is found that the interface roughness and microstructure, especially the crystallographic quality of the films have played key roles in determining the properties of NiFe/Cu/NiFe trilayers. With NiFeCr as buffer layer, antiferromagnetic coupling can be well established in the NiFe/Cu/NiFe trilayers, leading to an excellent GMR effect. The NiFe/Cu/NiFe trilayers with a NiFeCr buffer layer also exhibit a good thermal stability, making it suitable for sensing device applications.

Characterization of atomic-layer MoS2 synthesized using a hot filament chemical vapor deposition method*

Atomic-layer MoS2 ultrathin films are synthesized using a hot filament chemical vapor deposition method. A combination of atomic force microscopy (AFM), x-ray diffraction (XRD), high-resolution transition electron microscopy (HRTEM), photoluminescence (PL), and x-ray photoelectron spectroscopy (XPS) characterization methods is applied to investigate the crystal structures, valence states, and compositions of the ultrathin film areas. The nucleation particles show irregular morphology, while for a larger size somewhere, the films are granular and the grains have a triangle shape. The films grow in a preferred orientation (002). The HRTEM images present the graphene-like structure of stacked layers with low density of stacking fault, and the interlayer distance of plane is measured to be about 0.63 nm. It shows a clear quasi-honeycomb-like structure and 6-fold coordination symmetry. Room-temperature PL spectra for the atomic layer MoS2 under the condition of right and left circular light show that for both cases, the A1 and B1 direct excitonic transitions can be observed. In the meantime, valley polarization resolved PL spectra are obtained. XPS measurements provide high-purity samples aside from some contaminations from the air, and confirm the presence of pure MoS2. The stoichiometric mole ratio of S/Mo is about 2.0–2.1, suggesting that sulfur is abundant rather than deficient in the atomic layer MoS2 under our experimental conditions.

The Omnipolar Integrated Magnetic Switch Based on GMR

This paper presents the realization of omnipolar integrated magnetic switch based on GMR sensor, which was integrated with a specifically designed process IC by SiP technology. This integrated switch introduced hysteresis and adjustable sensitivity to improve its performance. When the gain was set to 2, its operation point and release point are 2.7|Oe| and 1.8|Oe| respectively. Its characteristics and function are verified by 2D Helmholtz coils and gear sensor test platform.

Effects of Different Relevant Layers on Magnetic Properties of Bottom Synthetic IrMn Spin Valves

The effects of different relevant layers, especially the insertion layers (which are between Ta buffer layer and IrMn pinning layer) and free layers, on the magnetic properties of IrMn bottom-pinning spin valves are investigated. Spin valve with a NiFe insertion layer exhibits a higher GMR ratio of ~ 6.0% than that of 2.0% for the spin valve with a Cu insertion layer due to a better pinning strength. The spin valves with a CoFe/NiFe composite free layer have relatively better magnetic properties: a higher GMR ratio compared with the spin valve with a single NiFe free layer and a lower free layer coercivity compared with the spin valve with a single CoFe layer.

Exchange Coupling in CrPtMn-based Top-pinning Spin Valves: Exchange Coupling in CrPtMn-based Top-pinning Spin Valves

The exchange coupling effect between the ferromagnetic pinned layer and antiferromagnetic pinning layer is considered to be one of the key factors for fabricating high performance spin-valves. In this study, the dependence of the exchange coupling field (Hex) in CrPtMn-based spin valves on the deposition pressure and subsequent anneal treatment has been investigated. It is found that the Hex for the as-deposited spin valves changes little by varying the sputtering pressure during the deposition of the CrPtMn pinning layer, and the Hex value is roughly 7.96×10 3 A/m. However, after the as-deposited spin valves are annealed at 240 ℃ for 2 h, the Hex correlates and increases with an in- crease of the sputtering pressure during the CrPtMn deposition. The exchange coupling Hex for annealed spin valves shows good thermal stability with a strength of 2.39×10 4 A/m at room temperature. The Hex gradually decreases with

Characterization of Integrated GMR Sensor with Angular Variation

In this work, GMR multilayer films are deposited and then processed into GMR sensors. The transfer curves of GMR sensor are acquired by sweeping the signal magnetic field in different directions. In addition, the rotation behavior is measured by rotating a magnitude-fixed field around the sensing axis. The results are analyzed and it’s found that the angular dependence of GMR sensor can be characteristic with cosine function.