Neuromorphic Computing with Emerging Antiferromagnetic Ordering in Spin-Orbit Torque Devices.

Field-free switching (FFS) and spin-orbit torque (SOT)-based neuromorphic characteristics were realized in a W/Pt/Co/NiO/Pt heterostructure with a perpendicular exchange bias () for brain-inspired neuromorphic computing (NC). Experimental results using NiO-based SOT devices guided the development of fully spin-based artificial synapses and sigmoidal neurons for implementation in a three-layer artificial neural network. This system achieved impressive accuracies of 91-96% when applied to the Modified National Institute of Standards and Technology (MNIST) image data set and 78.

Biological sensing using anomalous hall effect devices.

This paper outlines an approach to biological sensing involving the use of spintronic devices to sense magnetic particles attached to biological carriers. We developed an enzyme-linked immunosorbent assay (ELISA)-based Anomalous Hall Effect magnetic sensor via surface functionalization using Triethoxysilylundecanal (TESUD). The proposed sensor uses a CoFeB/MgO heterostructure with a perpendicular magnetic anisotropy.

Visualizing Ferroelectric Uniformity of HfZrO Films Using X-ray Mapping.

HfZrO (HZO) is a complementary metal-oxide-semiconductor (CMOS)-compatible ferroelectric (FE) material with considerable potential for negative capacitance field-effect transistors, ferroelectric memory, and capacitors. At present, however, the deployment of HZO in CMOS integrated circuit (IC) technologies has stalled due to issues related to FE uniformity. Spatially mapping the FE distribution is one approach to facilitating the optimization of HZO thin films.

Pulse-Driven Nonvolatile Perovskite Memory with Photovoltaic Read-Out Characteristics.

This paper presents a unique GdFeNiO perovskite thin film for use in pulse-controlled nonvolatile memory devices (combined with a SrTiO (STO) substrate) without the need for an electrical-stressing read-out process. The use of pulse voltage imposes permanent downward/upward polarization states on GFNO, which enables greater energy density and higher energy efficiency than the unpoled state for memory. The two polarization states produce carrier migrations in opposing directions across the GFNO/STO interface, which alter the depletion region of the device, as reflected in photovoltaic short-circuit current density () values.

GdFeNiO: A Multiferroic Material for Low-Power Spintronic Devices with High Storage Capacity.

Multiferroic materials are strong candidates for reducing the energy consumption of voltage-controlled spintronic devices because of the coexistence of ferroelectric (FE) and magnetic orders in a single phase. In this article, we present a new multiferroic perovskite, GdNiFeO (GFNO), produced via sputtering on a SrTiO substrate. The proposed GFNO is FE and canted antiferromagnetic (AFM) within a monoclinic framework at room temperature.

Heterostructured ferromagnet-topological insulator with dual-phase magnetic properties.

The introduction of ferromagnetism at the surface of a topological insulator (TI) produces fascinating spin-charge phenomena. It has been assumed that these fascinating effects are associated with a homogeneous ferromagnetic (FM) layer possessing a single type of magnetic phase. However, we obtained phase separation within the FM layer of a NiFe/BiSe heterostructure.

Voltage-induced Interface Reconstruction and Electrical Instability of the Ferromagnet-Semiconductor Device.

Using x-ray magnetic spectroscopy with in-situ electrical characterizations, we investigated the effects of external voltage on the spin-electronic and transport properties at the interface of a Fe/ZnO device. Layer-, element-, and spin-resolved information of the device was obtained by cross-tuning of the x-ray mode and photon energy, when voltage was applied. At the early stage of the operation, the device exhibited a low-resistance state featuring robust Fe-O bonds.

Phase-driven magneto-electrical characteristics of single-layer MoS2.

Magnetism of the MoS2 semiconducting atomic layer was highlighted for its great potential in the applications of spintronics and valleytronics. In this study, we demonstrate an evolution of magneto-electrical properties of single layer MoS2 with the modulation of defect configurations and formation of a partial 1T phase. With Ar treatment, sulfur was depleted within the MoS2 flake leading to a 2H (low-spin) → partial 1T (high-spin) phase transition.

Competing Anisotropy-Tunneling Correlation of the CoFeB/MgO Perpendicular Magnetic Tunnel Junction: An Electronic Approach.

We intensively investigate the physical principles regulating the tunneling magneto-resistance (TMR) and perpendicular magnetic anisotropy (PMA) of the CoFeB/MgO magnetic tunnel junction (MTJ) by means of angle-resolved x-ray magnetic spectroscopy. The angle-resolved capability was easily achieved, and it provided greater sensitivity to symmetry-related d-band occupation compared to traditional x-ray spectroscopy. This added degree of freedom successfully solved the unclear mechanism of this MTJ system renowned for controllable PMA and excellent TMR.

Low cost facile synthesis of large-area cobalt hydroxide nanorods with remarkable pseudocapacitance.

Large-area Co(OH)2-based supercapacitor electrodes composed of nanotube arrays grown on a 3D nickel-foam (CONTA) electrode and sucker-like nanoporous films grown on a 3D nickel-foam (COSNP) electrode were prepared with a facile electrochemical method for applications in energy storage. These nanoporous Co(OH)2 electrodes were fabricated with the codeposition of Cu/Ni film on the nickel foam, then etching of Cu from the Cu/Ni layer to form Ni nanotube arrays and sucker-like Ni nanoporous layers, and further cathodic deposition of Co(OH)2 on the prepared nanoporous Ni substrates. The CONTA and COSNP electrodes exhibited specific capacitances of 2500 and 2900 F/g in a voltage range of 0.

A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities.

An environmentally benign antisolvent method has been developed to prepare Cu(2+)-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility.

Instrument for x-ray absorption spectroscopy with in situ electrical control characterizations.

We report a synchrotron-based setup capable of performing x-ray absorption spectroscopy and x-ray magnetic circular dichroism with simultaneous electrical control characterizations. The setup can enable research concerning electrical transport, element- and orbital-selective magnetization with an in situ fashion. It is a unique approach to the real-time change of spin-polarized electronic state of a material/device exhibiting magneto-electric responses.

Direct probe of heterojunction effects upon photoconductive properties of TiO2 nanotubes fabricated by atomic layer deposition.

This study investigated Schottky- and ohmic-contact effects upon the photoresponses of ITO/TiO(2)/Si and Ti/TiO(2)/Si nanotube-based photodiodes. The TiO(2) tube arrays were fabricated by atomic layer deposition (ALD) and shaped by an anodic aluminum oxide (AAO) template on a p-type Si substrate. The contact area between the electrode (Ti or ITO) and the TiO(2)'s tip was varied by tuning the tube's inner wall thickness with ALD, providing a direct and systematic probe of the heterojunction effects upon the photodiodes' responses.

Superparamagnetic and ferromagnetic Ni nanorod arrays fabricated on Si substrates using electroless deposition.

The microstructures and magnetic properties of nickel nanorods fabricated using an anodic alumina oxide template and electroless deposition were investigated. The as-deposited nanorods were found to contain nanocrystalline grains with an average size of approximately 2-3 nm. The temperature-dependent magnetic hysteresis curves indicated superparamagnetic behavior of the as-deposited rods as a result of the reduction of ferromagnetic crystallites.

Pressure-induced magnetic transition in manganite (La0.75Ca0.25MnO3).

Low temperature Mn K-edge x-ray magnetic circular dichroism and x-ray diffraction measurements were carried out to investigate the stability of the ferromagnetic ground state in manganite La0.75Ca0.25MnO3 under nearly uniform compression using diamond anvil cells.

Pressure-induced electronic mixing and enhancement of ferromagnetic ordering in EuX (X=Te, Se, S, O) magnetic semiconductors.

The pressure- and anion-dependent electronic structure of EuX (X=Te, Se, S, O) monochalcogenides is probed with element- and orbital-specific x-ray absorption spectroscopy in a diamond anvil cell. An isotropic lattice contraction enhances the ferromagnetic ordering temperature by inducing mixing of Eu 4f and 5d electronic orbitals. Anion substitution (Te-->O) enhances competing exchange pathways through spin-polarized anion p states, counteracting the effect of the concomitant lattice contraction.

Novel pressure-induced magnetic transition in magnetite (Fe3O4).

Fe K-edge x-ray magnetic circular dichroism of magnetite (Fe3O4) powders was measured with synchrotron radiation under variable pressure and temperature conditions in diamond anvil cell. The magnetic dichroism was observed to decrease discontinuously by approximately 50% between 12 and 16 GPa, independent of temperature. The magnetic transition is attributed to a high-spin to intermediate-spin transition of Fe2+ ions in the octahedral sites and could account for previously observed structural and electrical anomalies in magnetite at this pressure range.