A seismic data acquisition system based on wireless network transmission is designed to improve the low-frequency response and low sensitivity of the existing acquisition system. The system comprises of a piezoelectric transducer, a high-resolution data acquisition system, and a wireless communication module. A seismic piezoelectric transducer based on a piezoelectric simply supported beam using PMN-PT is proposed. High sensitivity is obtained by using a new piezoelectric material PMN-PT, and a simply supported beam matching with the PMN-PT wafer is designed, which can provide a good low-frequency response. The data acquisition system includes an electronic circuit for charge conversion, filtering, and amplification, an FPGA, and a 24-bit analog-to-digital converter (ADC). The wireless communication was based on the ZigBee modules and the WiFi modules. The experimental results show that the application of the piezoelectric simply supported beam based on PMN-PT can effectively improve the sensitivity of the piezoelectric accelerometer by more than 190%, compared with the traditional PZT material. At low frequencies, the fidelity of the PMN-PT piezoelectric simply supported beam is better than that of a traditional central compressed model, which is an effective expansion of the bandwidth to the low-frequency region. The charge conversion, filtering, amplification, and digitization of the output signal of the piezoelectric transducer are processed and, finally, are wirelessly transmitted to the monitoring centre, achieving the design of a seismic data acquisition system based on wireless transmission.

This paper models, first, the eccentric installation of multiple sensors and inertial measurement unit (IMU), both dynamically and physically, based on the Simultaneous Localization and Mapping (SLAM) integrated navigation in the near-ground environment. Furthermore, the relationship between the estimated acceleration of other sensor locations under the eccentric motion and the actual measurement value of accelerometer has been analyzed. Most SLAM integrated navigation fusion algorithms incorporating IMU only accounts the transformation between the sensor coordinate systems, but avoids the Coriolis, tangential, and centrifugal forces caused by the eccentric rotation and the sensor installed at different locations. This problem affects the accuracy of the sensor acceleration estimated at different locations, and thus, affects the accuracy of the SLAM system pre-integration and the overall positioning accuracy of SLAM. Second, the eccentric correction optimization and pre-integration optimization algorithm have been implemented. Finally, a number of simulation experiments have been carried out to verify the optimal effect of the algorithm. The experimental results show that the positioning accuracy of the overall SLAM navigation algorithm can be effectively improved by eccentric correction optimization, and the RMSE of the optimized SLAM navigation algorithms has been reduced in varying degrees in different paths and algorithms. This study will be helpful for optimizing the positioning accuracy of SLAM and IMU integrated navigation scheme in the future.

The detection resolution of a giant magneto-impedance (GMI) sensor is mainly limited by its equivalent input magnetic noise. The noise characteristics of a GMI sensor are evaluated by noise modeling and simulation, which can further optimize the circuit design. This paper first analyzes the noise source of the GMI sensor. It discusses the noise model of the circuit, the output sensitivity model and the modeling process of equivalent input magnetic noise. The noise characteristics of three modules that have the greatest impact on the output noise are then simulated. Finally, the simulation results are verified by experiments. By comparing the simulated noise spectrum curve and the experimental noise spectrum curve, it is demonstrated that the preamplifier and the multiplier contribute the most to the output white noise, and the low-pass filter plays a major role in the output 1/f noise. These modules should be given priority in the optimization of the noise of the conditioning circuit. The above results provide technical support for the practical application of low-noise GMI magnetometers.

The current-induced perpendicular magnetization switching in $L1$ ₀ -FePt single layer and Ta/FePt bilayer thin films was investigated. Here, $L1$ ₀ -FePt (6 nm) single-layer film and Ta (1–5 nm)/FePt (6 nm) bilayer films were deposited on MgO substrate at 700 °C, showing good perpendicular anisotropy with out-of-plane coercivity of 7.5 kOe for FePt and around 5 kOe for Ta/FePt bilayers. It was found that the current-induced partial magnetization-based switching was realized with the spin–orbit torque (SOT) switching ratio of about 3% in all films. For adding the Ta capping layer, the critical current density is reduced and the stability of the switching loop is relatively better when compared to the single FePt layer. Furthermore, harmonic Hall voltage results demonstrate that the SOT efficiency ( $\beta _{\mathrm {DL}}$ ) of FePt single layer is approximately 50 Oe/(10 ⁷ A cm ⁻² ) and significantly higher than that of Ta/FePt bilayers, which is several times higher than that of the traditional Ta/CoFeB/MgO structure reported earlier. More importantly, Ta/FePt bilayer structure exhibits very good memristive switching behavior, which is expected to be applied to the spin-synapse of neural networks in the future.

Magnetic skyrmions have the potential for a wide range of applications in the next generation of spintronics since they are topologically protected spin configurations in the nanometer length scale. In order to be used in the logic gate, it is necessary to consider how to manipulate magnetic skyrmions. At present, the current drive is the mainstream drive, but this method could consume enormous energy for large Joule heating. In this work, the potential well is introduced to drive skyrmion to reduce energy consumption. The potential well is generated by voltage-controlled magnetic anisotropy (VCMA). We study the possibility of the potential well-induced skyrmion movement within a certain distance, the relevant factors that affect the distance of skyrmion induction, and propose a switched-voltage driving structure within the well-established framework of micromagnetics. Its processes have been theoretically investigated and demonstrated, in which the switched-voltage driving structure can be used to drive skyrmions. Our results provide guidance for the design of low energy consumption voltage-driven skyrmion driving method and a new concept for track memory.

The three-dimensional physical models for FeNi/Cu/FeNi films with two different types of structures which are linear and meander are developed. The relationship between the impedance of the films and the applied magnetic field or excitation frequency is obtained and the influence of geometric parameters and structures of the films on the giant magnetoimpedance (GMI) effect is analyzed. The result shows that the GMI effect in the film with a horizontal meander structure appears to be much stronger compared with that in a linear structure. The negative mutual inductance of the meander FeNi/Cu/FeNi films reduces the total inductance and decreases frequency response. Meanwhile, the GMI effect and the negative mutual inductance are enhanced by increasing the number of turns or decreasing the space width between each segment. Based on these effects, the FeNi/Cu/FeNi film with a vertical meander structure is proposed and simulated, which reflects the design of the meander structure in the thickness direction. The distance between each segment is reduced to 500 nm. The GMI effect and the negative mutual inductance are greatly enhanced (the maximum value of the GMI ratio increases from 207% to 1247% when the excitation frequency changes from 50MHz to 300MHz). Furthermore, the spatial resolution of the film is further improved. The results obtained could be useful both for a better understanding of the GMI effect of the FeNi/Cu/FeNi film with a meander structure and for providing a choice for the device preparation of highly sensitive magnetic sensors.