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Resistive random-access memory (RRAM) crossbar arrays have shown significant promise as drivers of neuromorphic computing, in-memory computing, and high-density storage-class memory applications. However, leakage current through parasitic sneak paths is one of the dominant obstacles for large-scale commercial deployment of RRAM arrays. To overcome this issue without compromising on the structural simplicity, the use of inherent selectors native to switching is one of the most promising ways to reduce sneak path currents without sacrificing density associated with the simple two-electrode structure. In this study, niobium oxide (NbO x ) was chosen as the resistive switching layer since it co-exhibits non-volatile memory and metal−insulatortransition selector behavior. Experimental results demonstrate abnormal phenomena in the reset process: a rapid decrease in current, followed by an increase when reset from the on state. The current conduction mechanism was examined through statistical analysis, and a conduction filament physical model was developed to explain the abnormal phenomenon. Under optimized operation conditions, non-linearity of ∼500 and fast switching speeds of 30 ns set and 50 ns reset were obtained. The switching behaviors with the intrinsic selector property make the NbO x device an attractive candidate for future memory and in-memory computing applications.

This article proposes a novel variable-flux spoke-type permanent magnet synchronous motor (VFS-PMSM), whose air gap flux density can be adjusted by "swiveling" magnetic pole directions in permanent magnet (PM). This is distinctive from conventional methods that require a large magnetizing field to magnetize and demagnetize (or partially) rotor PM along the same axis for variable flux motors. This paper first compares the proposed VFS-PMSM with two other typical types, i.e., series and parallel arrangements combining high-and low-coercivity PMs to achieve variable flux. It is found that the magnetic circuit of the proposed motor is identical to that of the series type at flux enhancing and to that of the parallel type at flux weakening. Therefore, the wide flux regulation range of the parallel type motors and the excellent on-load demagnetization-resisting capability of the series type motors can both be achieved in the proposed design. Another benefit of the proposed design is that the flux produced by the low-coercivity magnet constantly or aligns with that produced by the high-coercivity one whether the motor is flux enhanced or weakened. This allows the low-coercivity magnet to maintain its operating point within a safe range. These features make the proposed design suitable for electric vehicle tractions. Finite element analysis is used to compare the performance of various types of motors and highlight the advantages of the proposed VFS-PMSM. Experiments are conducted to validate the feasibility of the low-coercivity magnet to be magnetized with the method proposed in this paper. It is found that the field strength to magnetize or demagnetize the rotor can be significantly reduced, which improves the feasibility of this design.INDEX TERMS Electric vehicle, variable flux motor, magnetization, spoke type, permanent magnet synchronous motor.

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