Magnetoimpedance spectroscopy of phase-separated La0.5Ca0.5MnO3 polycrystalline manganites

Magnetoimpedance spectroscopy was carried out on phase-separated La_0.5Ca_0.5MnO₃ polycrystalline manganites. The La_0.5Ca_0.5MnO₃ powder was synthesized following an adapted sol-gel route. Structural and magnetic data showed the signs of phase coexistence of ferromagnetic (FM) Pnma and charge-ordered antiferromagnetic (CO-AFM) P2₁/m phases. Magnetization vs. temperature (M vs. T) measurements revealed several magnetic transitions from the high temperature paramagnetic (PM) to an FM phase upon cooling (PM-FM) at ≈240 K, FM-AFM (≈170 K) and AFM-FM (≈100 K). Magnetic field (H)-dependent impedance spectroscopy data were collected from sintered pellets and fitted with an equivalent circuit model to separately analyze the different dielectric contributions from the grain boundary (GB) and the grain interior bulk areas. This allowed separating the GB and bulk magnetoresistance (MR), which was shown to amount to a maximum of ≈80% for both GB and bulk at H = 10 T near the metal-insulator transition (MIT) at ≈100 K. The GB resistance was found to be larger than the bulk resistance by a factor of ≈3, which implies that the direct current (DC) resistance and DC MR are dominated by contributions from the GBs. The magnetocapacitance (MC) effects detected were all found to be small below ≈3%, including in the presence of a CO phase.

An Oxide Schottky Junction Artificial Optoelectronic Synapse

The rapid development of artificial intelligence techniques and future advanced robot systems sparks emergent demand on the accurate perception and understanding of the external environments via visual sensing systems that can co-locate the self-adaptive detecting, processing, and memorizing of optical signals. In this contribution, a simple indium-tin oxide/Nb-doped SrTiO₃ (ITO/Nb:SrTiO₃) heterojunction artificial optoelectronic synapse is proposed and demonstrated. Through the light and electric field co-modulation of the Schottky barrier profile at the ITO/Nb:SrTiO₃ interface, the oxide heterojunction device can respond to the entire visible light region in a neuromorphic manner, allowing synaptic paired-pulse facilitation, short/long-term memory, and "learning-experience" behavior for optical information manipulation. More importantly, the photoplasticity of the artificial synapse has been modulated by heterosynaptic means with a sub-1 V external voltage, not only enabling an optoelectronic analog of the mechanical aperture device showing adaptive and stable optical perception capability under different illuminating conditions but also making the artificial synapse suitable for the mimicry of interest-modulated human visual memories.

Reset Voltage-Dependent Multilevel Resistive Switching Behavior in CsPb1- xBi xI3 Perovskite-Based Memory Device

All-inorganic CsPb_{1- x}Bi _xI₃ perovskite film was successfully fabricated by incorporating Bi³⁺ in CsPbI₃ to stabilize the cubic lattice. Furthermore, the perovskite film was applied to manufacture a simple Ag/CsPb_{1- x}Bi _xI₃/indium tin oxide (ITO) memory device with a bipolar resistive switching behavior. Nonvolatile, reliable, and reproducible switching properties are demonstrated through retention and endurance test under fully open-air conditions. The memory device also presents highly uniform and long-term stable characteristics. Importantly, by modulating the reset stop voltages, multilevel high-resistance states are observed for the first time in lead halide perovskite memory device. The resistive switching behavior is proposed to explain the formation and partial rupture of conductive multifilament that are dominated by the migration of iodine ions and their corresponding vacancies in perovskite film. This study suggests Ag/CsPb_{1- x}Bi _xI₃/ITO device potential application for multilevel data storage in a nonvolatile memory device.

Resistive switching effects depending on Ni content in Au/NixPt(1−x) nanoparticle devices

NixPt_(1−x) nanoparticles were synthesized with x ranging from 1 to 0.7 and resistive switching effects depending on Ni contents were found in Au/NixPt_(1−x) nanoparticle devices.

Dielectric characteristics of Fe-doped LaTiO3+δ and visible light modulation

Fe-doped La_1−xFe_xTiO_3+δ (x = 0.05, 0.1, and 0.3, 0.4) ceramic samples were prepared via traditional solid-state reaction route, in which the dielectric properties of visible light modulation were found at room temperature in the measured frequency range.

Electric field effect dominated bipolar resistive switching through interface control in a Pt/TiO2/TiN structure

The field-enhanced effect due to the oxygen vacancy distribution improves the memory performance in the TiO₂-based RRAM device.

Synthesis and properties of single crystal TbMn2O5 nanostructures

Single crystal nanowire clusters of multiferroic material TbMn₂O₅ were obtained through a simple two-step method.