Pinched Hysteresis Loop Research Articles

A Novel Floating/Grounded Meminductor Emulator

Meminductor is a nonlinear two-terminal element with storage energy and memory ability. To date, meminductor element is not available commercially as memristor and memcapacitor are. Therefore, it is of great significance to implement a meminductor emulator for breadboard experiment. In this paper, a flux-controlled floating/grounded meminductor emulator without a memristor is presented. It is built with commercially available off-the-shelf electronic devices. It consists of single operational transconductance amplifier (OTA), single multiplier, two second-generation current conveyors (CCIIs), single current-feedback operational amplifier (CFOA) and single operational amplifier. Using OTA device introduces an additional control parameter besides frequency and amplitude values of applied voltage to control the area of pinched hysteresis loop of meminductor. Mathematical model of proposed emulator circuit is given to describe the behavior of meminductor circuit. The breadboard experiment is performed using CA3080, AD844, AD633J and LM741 for OTA, CCII–CFOA, multiplier and operational amplifier, respectively. Simulation and experimental test results are given to verify the theoretical analyses. Frequency-dependent pinched hysteresis loop is maintained up to 5 kHz. The presented meminductor emulator tends to work as ordinary inductor for higher frequencies.

Firing multistability in a locally active memristive neuron model

The theoretical, numerical and experimental demonstrations of firing dynamics in isolated neuron are of great significance for the understanding of neural function in human brain. In this paper, a new type of locally active and non-volatile memristor with three stable pinched hysteresis loops is presented. Then, a novel locally active memristive neuron model is established by using the locally active memristor as a connecting autapse, and both firing patterns and multistability in this neuronal system are investigated. We have confirmed that, on the one hand, the constructed neuron can generate multiple firing patterns like periodic bursting, periodic spiking, chaotic bursting, chaotic spiking, stochastic bursting, transient chaotic bursting and transient stochastic bursting. On the other hand, the phenomenon of firing multistability with coexisting four kinds of firing patterns can be observed via changing its initial states. It is worth noting that the proposed neuron exhibits such firing multistability previously unobserved in single neuron model. Finally, an electric neuron is designed and implemented, which is extremely useful for the practical scientific and engineering applications. The results captured from neuron hardware experiments match well with the theoretical and numerical simulation results.

A novel versatile window function for memristor model with application in spiking neural network

The memristor is a nano-size electrical device that is widely investigated in memory, logic circuits, and neuromorphic systems. This paper puts forward a general window function for Hewlett-Packard (HP) TiO2 memristor model, which covers almost all typical window functions and resolves the boundary lock problem, the inflexible parameter problem, and the distorted pinched hysteresis loop problem. Several adjustable parameters are introduced in the proposed window function in order to make it more flexible and scalable. A comparison with some classic window functions is given. Meanwhile, the range of these parameters is deduced with the aim of finding suitable parameters to simulate memristor devices. This TiO2 memristor model based on the novel window function is further applied to the spiking neural network and tested with the MNIST database of handwritten digits. The result demonstrates that the memristor-based neural network has higher recognition accuracy and better classification effect, indicating the availability of the entire scheme.

An interface-controlled Mott memristor in α -RuCl3

Memristor devices have history-dependent charge transport properties that are ideal for neuromorphic computing applications. We reveal a memristor material and mechanism in the layered Mott insulator α-RuCl3. The pinched hysteresis loops and S-shaped negative differential resistance in bulk crystals verify memristor behavior and are attributed to a nonlinear coupling between charge injection over a Schottky barrier at the electrical contacts and concurrent Joule heating. Direct simulations of this coupling can reproduce the device characteristics.

Room temperature magnetic biasing in Bi0.85La0.15FeO3 and BaTiO3 composite

In this study, the crystal structure and magnetic properties of two sets of multiferroic nanocomposites of Bi0.85La0.15FeO3 (BLFO) and BaTiO3 (BTO) were reported. The samples were prepared by adopting the conventional solid-state reaction and ball mill technique. The X-ray diffraction pattern and Raman spectra analysis reveal the impurity-free crystal structure, and both the phases (i.e., BLFO and BTO) are present in parallel in the nanocomposites. Scanning electron microscopy was used to study the surface morphology. The saturation magnetizations of the ball-milled nanocomposite are found to be significantly higher compared to that of the solid-state composites. The Vegard law was used to compare the observed saturation magnetization with the oretical values. The pinched hysteresis loop was observed in both sets of composites, which was explained by exchange type magnetic interaction between BLFO and BTO. The squareness ratio (R) tells the presence of intergrain magnetostatic interaction in the composites. The hysteresis loop width (ΔH) versus magnetization (M) plots for all the composites reveals the hysteresis loop anomalies.

New grounded and floating memristor emulators using OTA and CDBA

SummaryIn this paper, grounded and floating decremental/incremental memristor emulators have been proposed by using an operational transconductance amplifier (OTA), current differencing buffered amplifier (CDBA), and a grounded capacitor. The proposed memristor emulators are simpler in design over most of the realizations of memristor emulators available in the literature. The proposed configurations of grounded and floating decremental memristor emulators can be easily converted into grounded and floating incremental memristor emulators. The pinched hysteresis loops obtained from proposed memristor emulators are maintained up to 1‐MHz frequency in both decremental and incremental configurations. Simulation results have been obtained using a Mentor Graphics Eldo simulation tool in 0.18‐μm complementary metal‐oxide semiconductor (CMOS) technology parameters. Analog filters have also been designed to verify the performance of proposed grounded and floating memristor emulators.

Characteristics of analog memristor on thin-film Pt/Co0.2TiO3.2/ITO

In this work, thin films of Pt/Co0.2TiO3.2 (23 nm)/ITO were investigated showing their memristive capacity related to analog switching properties. A temporal analysis of current and voltage in nonlinear I–V graphs shows pinched hysteresis loop with gradual distribution in its electrical conductivity, typical of analog systems. The presence of trap centers such as oxygen vacancies suggests that the specific conduction mechanism is space-charge-limited current (SCLC). In addition, we study its performance under repetitive voltage pulses as well as at different durations. We further conducted data retention tests in the memristor high resistance state (HRS) and low resistance state (LRS).

A Multistable Generalized Meminductor with Coexisting Stable Pinched Hysteresis Loops

A multistable local active meminductor emulator is proposed in this paper. The mathematical model of the emulator circuits is established. Different periodic stimuli are applied to the presented emulators and coexisting stable pinched hysteresis loops are obtained. The results obtained by experimental equips are consistent with the theoretical analysis, which indicates that the proposed emulators can work as a meminductor.

Modeling of discrete fracmemristor and its application

Researches on the fracmemristor have aroused increasing interest in the last several years, but there are no reports on design of the discrete fracmemristor. Based on the fractional-order difference and the mathematical model of the charge-controlled memristor, the discrete fracmemristor is designed where the amount of charge is determined by a fractional-order discrete system. In the numerical simulations, it shows that the pinched hysteresis loops are observed, which imply that the proposed memristor satisfies the definition of the memristor. As an application, the fracmemristor sine map is designed, and multistability is observed regarding the initial conditions of both the memristor and system. It provides a potential model for different applications such as cellular neural networks, modulators, sensors, chaotic systems, and programmable digital circuits.

All Pinched Hysteresis Loops Generated by (α, β) Elements: in What Coordinates They May be Observable

Two existing theorems for studying pinched hysteresis loops generated by nonlinear higher-order elements from Chua's table are reformulated, namely the generalized homothety theorem and the associated Loop Location Rule, specifying the coordinates where the hysteresis may occur, and the ω <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> criterion theorem for computing the corresponding loop areas. It is demonstrated in this work that the pinched hysteresis loops are also generated in other coordinates than those predicted by the Loop Location Rule, and all these possible coordinates are found. The ω <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> criterion is generalized to computing the areas of all hysteresis loops that may be observable.

A Qualitative Study of Materials and Fabrication Methodologies for Two Terminal Memristive Systems

Though the concept of the thin film device, known by the name, memristors, as coined by Leon Chua, was theorized in 1971, it was only from the year 2008 that these thin film devices gained broader attention when R. Stanley Williams and his team demonstrated the first practical realization of the memristor at the HP labs . Memristors have been considered as the fourth fundamental circuit element, adding to resistors, capacitors and inductors. Among several other applications, the most unique application of memristors is that, while they occupy very little chip area, the synapses in the brain can be closely modeled using these devices. The memristive device from HP had two platinum electrodes on either side of a titanium dioxide (TiO2) and oxygen deficient titanium dioxide (TiO2-x) layers. The boundary separating the stoichiometric and oxygen deficient TiO2 regions can be shifted on either side under the effect of an applied electric field. The current-voltage characteristics of this device from HP Labs exhibited a pinched hysteresis loop with a zero-crossing, depicting high resistance and low resistance states distinctly. Since the discovery at HP labs, researchers have reported several material choices for the electrodes and the active region (TiO2 – TiO2-x). This paper presents a qualitative study on the material aspects of these nanoscale devices. Also, an exhaustive study of the different methodologies for fabricating such memristive systems is presented in this paper. These two terminal devices can be fabricated in a variety of ways but each method of fabrication has its own set of limitations since these devices operate at the nanoscale. The suitability of the single step and two step nano-imprint lithography (NIL) for memristors has been qualitatively examined in this paper

Questioning the Aloe Vera Plant and Apple Memristors.

Non-linear electrical properties of a (biological) tissue can be revealed by non-linear electrical measurements, which means that the applied stimulus itself affects the measurement. If resulting voltage–current plots exhibit pinched hysteresis loops, the underlying tissue may be classified as a memristor, a state dependent resistor. The aloe vera plant and apples have been found to be memristors. However, polarization processes on the electrodes are also non-linear and may affect the measurement. Apples and aloe vera conduct electrical current very well and it is likely that the recordings are actually dominated by the polarization impedance of the electrodes. Here, we study the non-linear properties of aloe vera and apples with two different measurement electrode types. Furthermore, we measured also on the extracted liquids from one aloe vera leaf and one apple, leading to similar results. We concluded, unlike previous studies on these subjects, that the memristive properties originate from electrochemical reactions on the electrodes rather than the apples or aloe vera themselves.

Information can be stored in the human skin memristor which has non-volatile memory

Much is already understood about the anatomical and physiological mechanisms behind the linear, electrical properties of biological tissues. Studying the non-linear electrical properties, however, opens up for the influence from other processes that are driven by the electric field or movement of charges. An electrical measurement that is affected by the applied electrical stimulus is non-linear and reveals the non-linear electrical properties of the underlying (biological) tissue; if it is done with an alternating current (AC) stimulus, the corresponding voltage current plot may exhibit a pinched hysteresis loop which is the fingerprint of a memristor. It has been shown that human skin and other biological tissues are memristors. Here we performed non-linear electrical measurements on human skin with applied direct current (DC) voltage pulses. By doing so, we found that human skin exhibits non-volatile memory and that analogue information can actually be stored inside the skin at least for three minutes. As demonstrated before, human skin actually contains two different memristor types, one that originates from the sweat ducts and one that is based on thermal changes of the surrounding tissue, the stratum corneum; and information storage is possible in both. Finally, assuming that different physiological conditions of the skin can explain the variations in current responses that we observed among the subjects, it follows that non-linear recordings with DC pulses may find use in sensor applications.

Memristive Behavior in Magnetic Elements Separated by Thin Non-Magnetic Spacer Layer

Memristance due to domain wall displacement following spin polarization of current through two magnetic elements with a thin non-magnetic spacer layer in between has been studied in this paper. A domain wall is a type of spin structure appearing between two magnetic domains. When spin polarized current interacts with the second layer it produces a change of resistance which depends on the relative orientation of the magnetic moments in layers. Analytical simulation results on 10 nm sample size domain wall have been obtained under the impression of magnetic field and spin polarization of current. The non-linear pinched hysteresis loop obtained as currentvoltage characteristics shows linearity at high frequencies.

A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics

Lead-free antiferroelectric silver niobate AgNbO3 ceramics have attracted growing interest for their superior energy storage density. The ceramics are commonly prepared by the conventional solid-state reaction method using Ag2O and Nb2O5 as the raw materials. An O2 atmosphere is maintained to prevent the possible decomposition of Ag2O during sintering, which increases the complexity of the process. In this work, we prepared successfully the pure phase AgNbO3 ceramics in air with the hydrothermally synthesized AgNbO3 powders. In comparison with the ceramics prepared by the conventional solid-state reaction method, the ceramics prepared by the hydrothermally synthesized powders have a broader antiferroelectric phase region and show pinched polarization-electric field hysteresis loops at moderate electric fields.

Nonstoichiometric charge defect induced relaxor antiferroelectric ordering in La modified Bi0.5 (Na0.80K0.20)0.5TiO3 relaxor ferroelectric

The effect of A-site nonstoichiometric in La3+ modified Bi0.5(Na0.80K0.20)0.5TiO3/BNKT solid solution on crystal structure and electrical properties have been investigated. Evolution of crystal structure from rhombohedral (R3c) to tetragonal (P4bm) symmetry with reduction of the lattice distortion has been observed. The Raman spectra analysis is well supported to the crystal structure study from the XRD patterns analysis. The presence of charge defects due to non-stoichiometric composition and the reduction of oxygen vacancies have been confirmed by the x-ray photoelectron spectra (XPS) of the respective elements. The FESEM (field emission scanning electron microscopy) micrographs clearly show the reduction of grain size with the incorporation of La3+ in A-site of BNKT. The multiple dielectric anomalies near depolarization temperature (Td) and temperature at maximum dielectric value (Tm) in the temperature dependent dielectric curves ascribe the diffuse phase transition with relaxor ferroelectric nature. The dielectric anomalies at Td and Tm become more pronounce with the increase in addition of La3+ into BNKT lattice. The presence of charge defects with A-sites complexity leads to interrupt the long range polar ferroelectric domains and, forms the polar nanoregions (PNRs). The competition between ferroelectric R3c symmetry and non-polar P4bm symmetry with the addition of La3+ into the BNKT lattice induces an intermediate modulated phase, which exhibits the antiferroelectric in nature having pinched ferroelectric hysteresis loop.

On the mechanism of creating pinched hysteresis loops using a commercial memristor device

In this short communication we analyze the impact of signal harmonics on the formation of the pinched hysteresis loop using a commercial memristor device. We show that by using only the fundamental frequency and the second harmonic components, extracted from the measured electrical current signal, a distortion-less pinched hysteresis loop is re-created. This loop is then used to simulate memristor-based AND/OR gates without any loss in digital functionality. This verifies that the generation of a pinched hysteresis loop requires a nonlinear frequency doubling mechanism to create a second harmonic in the current signal from an applied single frequency voltage excitation. Obtaining a pinched loop with three pinch points from the experimentally measured data is also demonstrated.

Memristor Emulator Circuit Using Multiple-Output OTA and Its Experimental Results

A charge-controlled memristor emulator circuit based on one kind of active device [operational transconductance amplifier (OTA)] using CMOS technology is introduced in this paper. The proposed circuit can be configured in both incremental and decremental types by using a simple switch. The memristor behavior can be electronically tuned by adjusting the transconductance of the OTAs. By changing the value of the capacitor, the pinched hysteresis loop observed in the current versus voltage plane can be held at higher frequencies. The proposed emulator circuit functions well up to 500 kHz. The experiment has been performed using commercially available OTA ICs (CA3080). The experimental demonstration has been carried out for 10, 20 and 120[Formula: see text]kHz. A simple high-pass filter is explained in both configurations to demonstrate the functionality of the proposed memristor emulator. The proposed circuit has been simulated in PSPICE using 0.5-[Formula: see text]m CMOS parameter. The simulated and experimental results validate the theoretical proposition.

Nanoelectrochemistry Concepts in Desalination Energy Harvesting and Analysis

This talk will provide an overview of the research in GWang’s group at Georgia State centered around the electrochemical processes at the nanometer scale. Three examples will be discussed in two research topics. The first is the development of new analytical method/toolbox for actively controlled nucleation and crystal growth. By controlling charge transport through a single nanopore, a single crystal is synthesized while the whole process is monitored by combined electroanalytical and optical methods. In the second topic, ion transport through a single asymmetric nanopipette is studied by experiments and simulation. The solution-substrate interface confined inside the conical nanopore is viewed as structurally-defined unit elements in ensemble porous membrane/electrode/materials. The surface electric field direction is separated from the through-transport ion flux which affects both the structure and dynamics of the electrical double layer (EDL). Selective and efficient transport of ions is the fundamental process in 1. the desalination with energy input; and a retrospective process of 2. energy harvesting from salinity when fresh and brackish/sea water mix. Novel time-dependent current-potential features are captured in electrochemical experiments due to the polarization of the nanoscale EDL or selective transport of ions. Characteristic signatures include a non-zero cross point in I-V curves separating pinched hysteresis loops. Finite element simulations by solving the Poisson, Nernst-Planck and Navier-Stokes equations reveal the respective transport of cations and anions driven by migration, diffusion and electroosmotic flow. The transport selectivity and efficiency under time- and space- confined conditions provide fundamental insights to better transport related applications such as desalination separation and energy harvesting from salinity gradients. Financial supports from NSF (CHE-1610616) and DOE (DE-SC0019043) are acknowledged.

Giant electro-strain and enhanced energy storage performance of (Y0.5Ta0.5)4+ co-doped 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 lead-free ceramics

0.94(Bi0.5Na0.5)(Y0.5Ta0.5)xTi1-xO3-0.06BaTiO3 lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method to study their excellent electro-strain properties and energy storage characteristics systematically. All ceramics exhibited a dense surface morphology. The introduction of (Y0.5Ta0.5)4+ complex ions destroyed the long-range ferroelectric order, which reduced the TF-R to the operating temperature, resulting in an easier field-induced transition between relaxor and ferroelectric phase. Therefore, for x = 0.01 component attained unipolar strain of 0.37% under 52 kV/cm, and the corresponding normalized strain d33* was 708 pm/V. Besides, the destruction of the ferroelectric phase also induced a pinched hysteresis loop and the maximum storage density of 1.215 J/cm3 with the efficiency of 68.7% obtained at 98 kV/cm for BNYT30 ceramics. These all demonstrated that the doping of complex ions (Y0.5Ta0.5)4+ made the BNT-BT an outstanding candidate for actuators and energy storage devices.