Miaocheng Zhang

Bio: Miaocheng Zhang is an academic researcher from Nanjing University of Posts and Telecommunications. The author has contributed to research in topics: Memristor & Neuromorphic engineering. The author has an hindex of 4, co-authored 17 publications receiving 950 citations.

Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

Resistance switching characteristics and mechanisms of MXene/SiO2 structure-based memristor

Abstract: Silicon dioxide memristors possess multiple resistance states and can be used as a key component of memory devices and neuromorphic systems. However, their conductive mechanisms are incompletely understood, and their resistance switching (RS) variability is a major challenge for commercialization of memristors. In this work, by combining the desirable properties of silicon dioxide with those of a two-dimensional MXene material (Ti3C2), a memristor based on an MXene/SiO2 structure is fabricated. The Cu/MXene/SiO2/W memristive devices exhibit excellent switching performance compared with traditional Cu/SiO2/W devices under the same conditions. Furthermore, the role of the MXene/SiO2 structure in the SiO2-based memristors is revealed by the physical characterization of the MXene and first-principles calculation of the MXene/SiO2 structure. The results indicate that the conductive filaments (CFs) are more likely to grow along the locations of MXene nanostructures, which reduces the randomness of CFs in the Cu/MXene/SiO2/W memristors and further improves the device performance. Meanwhile, the MXene/SiO2 structure appears to greatly reduce the mobility of Cu ions in the entire RS region, as well as improve the performance of the SiO2-based memristors while maintaining the operating voltages low.

Manipulation of the electrical behaviors of Cu/MXene/SiO2/W memristor

Abstract: Electronic synapses with both long-term and short-term plasticity are considered as significant components for constructing brain-inspired computing systems. Research progress on electrical synapses have proved that memristors possess huge similarities with biological synapses. Nevertheless, an effective mean of manipulating the biological properties of memristors is still unclear. In this letter, we propose a memristor and reveal that the compliance current of electroforming plays an active role in tuning short-term and long-term plasticity of the memristors. The results may provide a useful guideline for manipulating memristor as electronic synapses in the hardware implementation of artificial neural networks.

Multiferroicity: the coupling between magnetic and polarization orders

Abstract: Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review, we outline some of the progressive milestones in this stimulating field, especially for those single-phase multiferroics where magnetism and ferroelectricity coexist. First, we highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we summarize various strategies used to combine the two types of order. Special attention is paid to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry; (2) the ferroelectricity originating from the charge-ordered states; and (3) the ferrotoroidic system. Then, we address the elementary excitations such as electromagnons, and the application potentials of multiferroics. Finally, open questions and future research opportunities are proposed.

First-principles study of spontaneous polarization in multiferroic Bi Fe O 3

Abstract: The ground-state structural and electronic properties of ferroelectric $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ are calculated using density functional theory within the local spin-density approximation (LSDA) and the $\mathrm{LSDA}+U$ method. The crystal structure is computed to be rhombohedral with space group $R3c$, and the electronic structure is found to be insulating and antiferromagnetic, both in excellent agreement with available experiments. A large ferroelectric polarization of $90--100\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{C}∕{\mathrm{cm}}^{2}$ is predicted, consistent with the large atomic displacements in the ferroelectric phase and with recent experimental reports, but differing by an order of magnitude from early experiments. One possible explanation is that the latter may have suffered from large leakage currents. However, both past and contemporary measurements are shown to be consistent with the modern theory of polarization, suggesting that the range of reported polarizations may instead correspond to distinct switching paths in structural space. Modern measurements on well-characterized bulk samples are required to confirm this interpretation.

Greatly reduced leakage current and conduction mechanism in aliovalent-ion-doped BiFeO3

Abstract: Transport properties of aliovalent-ion-doped BiFeO3 (BFO) thin films have been studied in order to identify the cause of high leakage currents Doping of 2at% Ti4+ ions increased the dc resistivity by more than three orders of magnitude In contrast, doping of 2+ ions such as Ni2+ reduced the dc resistivity by two orders of magnitude Current–voltage (I–V) characteristics indicated that the main conduction mechanism for pure and Ni2+ doped BFO was space charge limited, which was associated with the free-carriers trapped by the oxygen vacancies, whereas in the Ti4+ doped BFO, field-assisted ionic conduction was dominant

Visible-Light Photocatalytic Properties of Weak Magnetic BiFeO3 Nanoparticles

Abstract: Polycrystalline BiFeO3 nanoparticles (size 80-120 nm) are prepared by a simple sol-gel technique. Such nanoparticles are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies. The BiFeO3 nanoparticles also demonstrate weak ferromagnetism of about 0.06 mu(B)/Fe at room temperature, in good agreement with theoretical calculations.

The single-phase multiferroic oxides: from bulk to thin film

Abstract: Complex perovskite oxides exhibit a rich spectrum of properties, including magnetism, ferroelectricity, strongly correlated electron behaviour, superconductivity and magnetoresistance, which have been research areas of great interest among the scientific and technological community for decades. There exist very few materials which exhibit multiple functional properties; one such class of materials is called the multiferroics. Multiferroics are interesting because they exhibit simultaneously ferromagnetic and ferroelectric polarizations and a coupling between them. Due to the nontrivial lattice coupling between the magnetic and electronic domains (the magnetoelectric effect), the magnetic polarization can be switched by applying an electric field; likewise the ferroelectric polarization can be switched by applying a magnetic field. As a consequence, multiferroics offer rich physics and novel devices concepts, which have recently become of great interest to researchers. In this review article the recent experimental status, for both the bulk single phase and the thin film form, has been presented. Current studies on the ceramic compounds in the bulk form including Bi(Fe,Mn)O3, REMnO3 andthe series of REMn2O5 single crystals (RE = rare earth) are discussed in the first section and a detailed overview on multiferroic thin films grown artificially (multilayers and nanocomposites) is presented in the second section.