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Abstract: Ferroic‐order‐based devices are emerging as alternatives to high density, high switching speed, and low‐power memories. Here, multi‐nonvolatile resistive states with a switching speed of 6 ns and a write current density of about 3 × 103 A cm−2 are demonstrated in crossbar‐structured memories based on all‐oxide La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions. The tunneling resistive switching as a function of voltage pulse duration time, associated with the ferroelectric domain reversal dynamics, is ruled by the Kolmogorov–Avrami–Ishibashi switching model with a Lorentzian distribution of characteristic switching time. It is found that the characteristic resistance switching time decreases with increasing voltage pulse amplitude following Merz's law and the estimated write speed can be less than 6 ns at a relatively higher voltage. These findings highlight the potential application of multiferroic devices in high speed, low power, and high‐density memories. [ABSTRACT FROM AUTHOR]

Sub‐nanosecond (≈540 ps) resistive switching with high off/on resistance ratio is demonstrated in an Au/YIG/n‐Si resistive random access memory (RRAM) at room temperature and 85 °C in article number 1800418 by Yuewei Yin, Xiaoguang Li, and co‐workers. Five discrete resistance levels with ultrafast switching clearly show reliable retentions. Such an RRAM is promising for next‐generation non‐volatile memories with ultrahigh speed, low power consumption, and high density. [ABSTRACT FROM AUTHOR]

Resistive random access memory (RRAM) with ultrafast and multilevel switching is extremely promising for next‐generation nonvolatile memory. Here, ultrafast unipolar resistive switchings (≈540 ps) with high off/on resistance ratio (≈104) are obtained in yttrium iron garnet Y3Fe5O12 (YIG)‐based resistive memory on n‐Si substrate. The sub‐nanosecond operation is also successfully performed up to 85 °C with an off/on resistance ratio of ≈103. In addition, by using different compliance currents for the set process, five discrete resistance levels with ultrafast switchings among them are achieved and the multilevel states show reliable retention (>104 s). The large, stable, reproducible, and reliable switching behaviors of the Au/YIG/n‐Si RRAM cell shows its great potential for ultrafast multilevel memory applications. By fabricating an Au/YIG/n‐Si resistive random access memory (RRAM) on silicon, ultrafast unipolar resistive switchings (≈540 ps) with high off/on resistance ratio are demonstrated at both room temperature and 85 °C. Five discrete resistance levels with ultrafast switchings are obtained and show reliable retention. Such an ultrafast multilevel unipolar RRAM is promising for ultrafast multilevel memory applications. [ABSTRACT FROM AUTHOR]

Electric-field control of magnetism is a key issue for the future development of low-power spintronic devices. By utilizing the opposite strain responses of the magnetic anisotropies in Co and Ni films, a Co/Cu/Ni/0.7Pb(Mg 1/3 Nb 2/3 )O 3 -0.3PbTiO 3 (PMN-PT) spin-valve/piezoelectric heterostructure with ∼7 nm Cu spacer layer was properly designed and fabricated. The purely electric-field-controlled nonvolatile and reversible magnetization rotations in the Co free layer were achieved, whereas the magnetization of the Ni fixed layer was almost unchanged. Accordingly, not only the electroresistance but also the electric-field-tuned magnetoresistance effects were obtained, and more importantly at least six nonvolatile magnetoresistance states in the strain-tuned spin valve were achieved by setting the PMN-PT into different nonvolatile piezo-strain states. These findings highlight potential strategies for designing electric-field-driven multistate spintronic devices.

Brain-inspired computing architectures attempt to emulate the computations performed in the neurons and the synapses in the human brain. Memristors with continuously tunable resistances are ideal building blocks for artificial synapses. Through investigating the memristor behaviors in a La 0.7 Sr 0.3 MnO 3 /BaTiO 3 /La 0.7 Sr 0.3 MnO 3 multiferroic tunnel junction, it was found that the ferroelectric domain dynamics characteristics are influenced by the relative magnetization alignment of the electrodes, and the interfacial spin polarization is manipulated continuously by ferroelectric domain reversal, enriching our understanding of the magnetoelectric coupling fundamentally. This creates a functionality that not only the resistance of the memristor but also the synaptic plasticity form can be further manipulated, as demonstrated by the spike-timing-dependent plasticity investigations. Density functional theory calculations are carried out to describe the obtained magnetoelectric coupling, which is probably related to the Mn-Ti intermixing at the interfaces. The multiple and controllable plasticity characteristic in a single artificial synapse, to resemble the synaptic morphological alteration property in a biological synapse, will be conducive to the development of artificial intelligence.

Solid-state dielectric film capacitors with high-energy-storage density will further promote advanced electronic devices and electrical power systems toward miniaturization, lightweight, and integration. In this study, the influence of interface and thickness on energy storage properties of SrTiO 3 (STO) films grown on La 0.67 Sr 0.33 MnO 3 (LSMO) electrode are systematically studied. The cross-sectional high resolution transmission electron microscopy reveals an ion interdiffusion layer and oxygen vacancies at the STO/LSMO interface. The capacitors show good frequency stability and increased dielectric constant with increasing STO thickness (410-710 nm). The breakdown strength (E b ) increases with decreasing STO thickness and reaches 6.8 MV/cm. Interestingly, the E b under positive field is enhanced significantly and an ultrahigh energy density up to 307 J/cm 3 with a high efficiency of 89% is realized. The enhanced E b may be related to the modulation of local electric field and redistribution of oxygen vacancies at the STO/LSMO interface. Our results should be helpful for potential strategies to design devices with ultrahigh energy density.