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Skyrmion-based devices are an attractive candidate for nonvolatile memory and low-power computation. In a real device, however, skyrmions easily annihilate at device edges, which hampers device applications. Here, we present a novel skyrmion-based logic device, which takes advantage of the skyrmion annihilation (SA) and increases the efficiency of logic operation. An SA half adder (HA) is implemented in a ferromagnet/heavy metal nanotrack by introducing a geometric notch that annihilates the skyrmion. In addition, full adder and n-bit SA ripple-carry adder are demonstrated by directly cascading the SA HAs. The prototype of a 32-bit SA ripple-carry adder consumes energy as low as 0.62 pJ per each operation, which is only 18% of the previously proposed skyrmion adder. Our SA logic gate can, therefore, be a promising candidate for the beyond-CMOS logic device. [ABSTRACT FROM AUTHOR]

This paper presents the electromagnetic analysis and experimental testing of a tubular linear synchronous machine (TLSM) with a double-sided axially magnetized permanent magnet (AMPM) mover and coreless stator winding by using semianalytical techniques. Using a simple result based on the finite element method (FEM), characteristics of the TLSM with AMPM can be calculated with the semianalytical method easily. The magnetic flux density in the air gap is obtained by using a magnetic vector potential, a 2-D polar coordinate system, and the results of the magnetostatic calculation based on FEM. Based on these solutions, the electromotive force (EMF) is also determined analytically. Then, 2-D FEM is employed to validate the semianalytical method. Finally, experimental testing of the EMF measurements is performed to confirm the results of the semianalytical techniques. [ABSTRACT FROM AUTHOR]