Antiferromagnets (AFMs) are ideal materials to boost neuromorphic computing toward the ultrahigh speed and ultracompact integration regime. However, developing a suitable AFM neuromorphic memory remains an aspirational but challenging goal. In this work, we construct such a memory based on the CoO/Pt heterostructure, in which the collinear insulating AFM CoO shows a strong perpendicular anisotropy facilitating its electrical readout and writing. Utilizing the unique nonlinear response and bipolar fading memory properties of the device, we demonstrate a multidimensional reservoir computing beyond the traditional binary paradigm. These results are expected to pave the way toward next-generation fast and massive neuromorphic computing.
We present a diffractive method for obtaining azimuthal and radially polarized beams. This method involves a modified half-wave plate, a composite spiral zone plate, a pinhole and a lens. Two composite spiral zone plates are combined and assisted by a pinhole and a lens, to transform a circularly polarized beam into a radially polarized or an azimuthal polarized beam. This method is investigated numerically using diffraction theory. The field distributions on the focal spot of the composite spiral zone plates and the output cylindrical beams are calculated. Finally, the use of this method to generate cylindrical vector beams is validated.
The fact that in organic semiconductors the Hubbard energy is usually positive appears to be at variance with a bipolaron model to explain magnetoresistance (MR) in those systems. Employing percolation theory, we demonstrate that a moderately positive $U$ is indeed compatible with the bipolaron concept for MR in unipolar current flow, provided that the system is energetically disordered, and the density of states (DOS) distribution is partially filled, so that the Fermi level overlaps with tail states of the DOS. By exploring a broad parameter space, we show that MR becomes maximal around $U=0$ and even diminishes at large negative values of $U$ because of spin independent bipolaron dissociation. Trapping effects and reduced dimension enhance MR.
In order to solve the problems of information loss in image fusion, an infrared and visible image fusion method based on fractional-order differentiation is proposed. Firstly, the multi-scale transform is used to decompose the source images into low frequency and high frequency subbands, and the low frequency subbands are further decomposed into low frequency basic subbands and low frequency detail subbands by two-scale decomposition. Secondly, for the low frequency base subbands, the weighted sum of energy ratio and standard deviation ratio is used to construct the judgment value which is used to fuse low frequency base subbands. For low frequency detail subbands and high frequency subbands, the fractional-order differentiation is introduced, and the fusion rule of maximum fractional-order sum of modified laplacian is adopted. Finally, the fused low-frequency basic subband and low-frequency detail subband are transformed by two-scale inverse transformation to obtain the fused low-frequency subband. the multi-scale inverse transformation is performed to the fused low frequency subband and high frequency subbands to obtain the fused image. Three groups of infrared and visible images are selected to verify the effectiveness of the proposed algorithm. From the subjective assessments, the proposed method highlights the infrared target well, retains the details of the visible image and texture details, and achieves a good visual effect. From the objective assessments, the entropy, standard deviation, spatial frequency and mean gradient of the fusion method in this paper are higher than the other five methods.
Binary phase square spiral zone plates (BPSSZPs), a special type of binary phase vortex lenses, are introduced to generate focused optical vortices showing square symmetry. The numerical solution and fabrication method, as well as the experimental results are given. Different from conventional vortex lenses, these BPSSZPs produce focused vortices with small topological charge following a modulo-4 transmutation rule. In addition, the central diffracted image rotates in the vicinity of the focal plane. These interesting properties suggest that BPSSZPs might become key components for many potential applications such as optical image processing and quantum computation.
Cycloaliphatic epoxy resin containing hydroxyl group (DMTMP) was prepared by the transesterification between methyl-3,4-epoxycyclohexane carboxylate (MEC) and trimethylolpropane (TMP), which was then thermally cured with methylhexahydrophthalic anhydride (MHHPA). As comparison, a commercial available cycloaliphatic epoxy 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (ERL-4221) cured with the same curing agent was also investigated. The chemical structure was characterized by FT-IR and 1H-NMR. And the curing behavior and the thermal properties were studied by DSC and TGA. The DSC results showed that the DMTMP systems exhibited higher reactivity than the ERL-4221 systems due to the autocatalysis of hydroxyl group of DMTMP. While the glass temperature transitions (Tg s) of DMTMP systems were much lower than ERL-4221 systems, and the Tg s of DMTMP and ERL-4221 systems both reduced after introducing n-dodecyl trimethylammonium bromide (DTAB) as catalyst. The decomposition behavior from TGA shows that the DMTMP epoxy resins exhibited a relative slow weight decreasing tendency in comparison with ERL-4221 epoxy resins, but initial degradation temperatures of DMTMP systems were lower than ERL-4221 systems.
Conventional diffraction gratings composed of a series of equally spaced slits suffer from wavelength overlapping caused by high-order diffraction. Here modulated groove position gratings (MGPGs) are proposed to significantly suppress the high diffraction orders. Both numerical solution and experimental results demonstrate the effectiveness of MGPGs. The suppression ratio is determined by the number of grating grooves used. By using an MGPG with 10,000 grooves, a suppression ratio as high as 18,000 can be obtained. In addition, the minimum linewidth is kept to 1/4 of the grating period, which enables grating realization with high line density employing today's nanofabrication technology. Our results should be of great interest in both diffraction grating theory and applications, particularly due to MGPGs' applicability in a wide wavelength range and realizability with high line density.
Electrical manipulation of the topological charges of magnetic vortices is of vital importance for the development of vortex-based devices. Here, we show that the spin–orbit torque (SOT) effect can be employed to deterministically and selectively annihilate the vortex core, and this process exhibits a symmetry that is consistent with that of the SOT-induced magnetization switching in perpendicularly magnetized systems. By changing the SOT current pulse direction, it is also possible to write back a vortex with random topological charges from the quasi-single-domain state after annihilation. These intriguing results can be utilized as a random topological charge generator and applied in stochastic computing where a tunable random stream source plays a central role.
In this work, we present the fabrication process of a large area (100mm×40mm) and thick (30mm) single order diffraction grating for a 10-1000eV soft X-ray monochromator. Three types of diffraction gratings were integrated on one single piece of bulk silicon. The gratings were patterned on a 4 inch silicon wafer using direct e-beam writing with SAL-601. The wafer was etched and diced into a 100mm×40mm×0.5mm slice, and this slice is bonded to a bulk silicon using low temperature Au-Au bonding technology. The performance of this grating is tested in soft X-ray region.
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