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The synthesis of low-cost and high electrochemical activity to regenerate electrolyte and to enhance the efficiency (counter electrodes (CE)) is of paramount importance for the DSSCs. To achieve the maximum power conversion efficiency of DSSCs with the low-cost counter electrode (CE), Cu– (In, Co, Ni, Mn)–Se2 has prepared by hydrothermal method. The structural and chemical composition of Cu– (In, Co, Ni, Mn)–Se2 was confirmed by XRD and XPS analysis. The charge transfer resistance of CuInSe2 (CIS), CuCoSe2 (CCS), CuNiSe2 (CNS), and CuMnSe2 (CMS) were 5.60, 11.50, 1.40, and 5.60 Ω (CNS

New hierarchical quaternary Cu2NiSnS4 nanostructures were successfully synthesized by a facile hydrothermal method using different surfactants. The crystal structure, elemental composition and morphologies of the as-synthesized nanostructures were characterised by XRD, XPS and FESEM as well as TEM respectively. The charge transfer resistance, catalytic and photovoltaic performance of Cu2NiSnS4 exhibited morphological dependence. The nanosheet based flower like hierarchical structure formed in the presence of ethylenediamine exhibited favourable electrocatalytic properties when used as counter electrode in DSSC with an overall conversion efficiency of 3.86 % with a fill factor of 65 %, a short circuit current of 8.02 mA cm2 which were comparable with those of Pt (3.93 %), fill factor of 66 %, a short circuit current of 8.23 mA cm2 under the same device configuration.

Low energy density of the supercapacitors is considered as a roadblock for its application in or as a primary power source. While, utilization of high energy density battery-type electrode materials in an asymmetrical configuration was expected to resolve this hurdle, however, its inferior rate performance and poor cycling stability hinder the overall device performance. Incomplete utilization of active material at elevated current density was identified as the root for poor rate performance. Herein, we developed a hierarchical NiS microspheres build by the self-assembly of hexagonal nanoplates via trimethylamine (TEA) assisted hydrothermal method. The optimized sample exhibited a superior specific capacitance of 606 C/g at 0.5 A/g. More interestingly, the electrode was able to retain 50% (302 C/g at 20 A/g) of its maximum capacity even when the current density was multiplied 40-fold relative to 18% (50 C/g at 20 A/g) shown by control sample prepared without TEA. Excellent rate performance of the electrode could be attributed to the increment in the electrolyte-accessible surface area by morphological modifications. Owing to its porous nature, optimized sample was able to retain 93% of its original capacity at the end of 2000 continuous cycles of charge-discharge. Furthermore, an asymmetric supercapacitor with NiS-C as the positive electrode and activated carbon as the negative electrode delivered a high energy density of 35.07 Wh/kg at a power density of 0.420 kW/kg within an operating voltage window of 1.5 V.

600 mV magneto-electric switching in 30 nm La-doped BiFeO 3 multiferroic oxide and a proof of concept 7 μV spin-orbit signal output in Pt / CoFe local spin injection device with 100 μA supply current were experimentally demonstrated at room temperature for the 1st time. Also demonstrated was a path towards 70 mV spin orbit output using Bi 2 Se 3 in a local spin injection device. These are key accomplishments for WRITE and READ building blocks, respectively, toward realization of a magneto-electric spin-orbit (MESO) energy-efficient logic device. Moreover, the 1st generation of a MESO logic device with a functional READ unit is demonstrated.

In the present work, spinel Ni(1−X)CrXFe2O4 (X = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 M) nanoparticles were synthesized by co-precipitation method followed by calcination at 400 °C for 2 h. The structural and morphological properties of the synthesized nanoparticles were studied using powder XRD,micro-Raman measurements, FE-SEM, TEM and EDS. The results revealed that the synthesized nanoparticles were single-crystal, cubic-phase structure with spherical shape. Energy-dispersive X-ray spectroscopy confirmed the elements present in the synthesized nanoparticles. Moreover, microwave absorption properties were measured using vector network analyser (VNA). The minimum reflection loss − 14.44 dB at 9.49 GHz was observed for Ni(1−X)CrXFe2O4 (X = 0.5 M) nanoparticles at 3 mm thickness. These results suggest that Ni(1−X)CrXFe2O4 (X = 0.5 M) nanoparticles would be applicable for microwave absorption application.

In the present work, spindle-shaped ZnO and reduced graphene oxide sheets were successfully synthesized by a hydrothermal method and then ZnO/r-GO composite was prepared by a direct solution mixing method. Various characterization results confirmed the interior and surface decoration of spindle-shaped ZnO on the reduced graphene oxide sheets. The phase formation, crystalline structure, morphology, surface states and optical properties were characterized using Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and UV–Vis spectroscopy. The X-ray diffraction analysis showed the formation of the hexagonal wurtzite crystalline structure of ZnO with high crystalline quality. The band gap of the ZnO/r-GO composite was found to be low (3.03eV) compared to the band gap of spindle shaped ZnO (3.13 eV), as calculated from optical studies. The spindle-like morphology of the single crystalline ZnO was clearly shown in the electron microscopic images. The chemical bonding and surface states of the samples were studied using XPS measurement. Moreover, a possible growth mechanism for the ZnO spindle was proposed. The catalytic activity of the as-synthesized samples was evaluated for the photodegradation of methylene blue under visible light irradiation. Among the synthesized samples, the ZnO/r-GO composite showed higher degradation efficiency of 93% and successfully reused for four consecutive run without any activity loss.

The ultimate challenge for the development of new multiferroics with enhanced properties lies in achieving nanoscale control of the coupling between different ordering parameters. In oxide-based multiferroics, substitutional cation dopants offer the unparalleled possibility to modify both the electric and magnetic properties at a local scale. Herein it is demonstrated the formation of a dopant-controlled polar pattern in BiFeO3 leading to the spontaneous instauration of periodic polarization waves. In particular, nonpolar Ca-doped rich regions act as spacers between consecutive dopant-depleted regions displaying coupled ferroelectric states. This alternation of layers with different ferroelectric state creates a novel vertical polar structure exhibiting giant polarization gradients as large as 70 μC cm–2 across 30 A thick domains. The drastic change in the polar state of the film is visualized using high-resolution differential phase-contrast imaging able to map changes in ferroelectric polarization at at...

Background: Vascular injury is the initial event in the pathogenesis of systemic sclerosis (SSc) and potent proangiogenic mediators such as vascular endothelial growth factor (VEGF) are overexpressed in the skin and circulation of patients with SSc. The objective of this study was to determine the serum levels of VEGF in patients with SSc and to correlate it with the severity of skin thickening, digital ischemia, and interstitial lung disease (ILD). Methods: Serum VEGF levels were measured in 55 patients with SSC who fulfilled 2013 ACR/EULAR classification criteria for scleroderma and 30 healthy age- and gender-matched controls by ELISA. All patients underwent detailed clinical examination, baseline blood investigations, chest X-ray, electrocardiogram, and pulmonary function tests. Echocardiography and high-resolution computed tomography scan of lungs were done wherever necessary. Results: Median serum VEGF in SSc patients was higher than in the controls (675 pg/ml [interquartile range (IQR): 395–920] vs. 180.5 pg/ml [IQR: 155–215], respectively; P = 0.00001). No statistically significant difference was observed between diffuse (662.5 pg/ml [IQR: 441.25–942.5]) and limited SSc (680 pg/ml [IQR: 325–850]) (P = 0.412). Serum VEGF levels correlated significantly with higher modified Rodnan skin scores (r = 0.7168) (P < 0.0001) and lower forced vital capacity (r = −0.6771) (P < 0.0001). Median VEGF levels were higher in patients with digital ischemia (digital pitted scars, digital ulcers, and gangrene) compared to those without ischemic changes (P = 0.001). Patients with ILD (n = 21) had significantly higher median VEGF levels when compared to those without ILD (n = 34) (870 pg/ml [IQR: 592.5–1000] vs. 467.5 pg/ml [IQR: 297.5–760]; P = 0.001). There was no significant difference in serum VEGF levels between early (650 pg/ml [IQR: 375–885]) and late stages (890 pg/ml [IQR: 530–1000]) of disease (P = 0.197). Conclusion: Serum VEGF levels were elevated in SSc and they correlated with the severity of skin thickening, digital ischemia, and presence of ILD.

The polyindole/Graphitic carbon nitride (PIn/g-C3N4) composites synthesized by the reflux method. The characterization results showed that the composites possess balanced porosity, good charge diffusion, high energy and power densities. PIn/g-C3N4 composite showed the specific capacity (QS) of 440.8 C/g at 6 A/g in 1 mol/L aqueous H2SO4 electrolyte. The asymmetric device of PIn/g-C3N4//rGO showed QS of 73.84 C/g at 3 A/g. PIn/g-C3N4//rGO device offered a moderate cyclic retention of 72% at 18 A/g after 5,000 cycles with an energy density of 23.2 Wh/Kg and power density of 2307 W/Kg at 3 A/g. The results demonstrated that PIn/g-C3N4 composite has a potential application in field of energy storage devices.

In the present work, we have performed Raman spectral analysis, scanning electron microscopic analysis and electrochemical measurements of dynamic shock wave loaded cobalt ferrite nano-particles (CoFe2O4 NPs) for different number of shock pulses as that of 0, 50,100 and 150 such that the respective observations have been investigated and the results are reported. Interestingly, among the four samples, 50 shocks loaded sample has homogenous particle size distribution and a high value of specific capacitance due to the occurrence of the shock wave-induced dynamic re-crystallization. Based on the observed electrochemical properties, shock wave loaded CoFe2O4 NPs are strongly suggested for energy storage applications.

Here in, ZnO sphere/r-GO composites was synthesized by a simple hydrothermal method. The morphological characterizations (FE-SEM and TEM) indicated the ZnO sphere covered by r-GO nanosheets. The formation of the prepared ZnO sphere/r-GO composites was investigated by XRD and FT-IR analytical techniques, respectively. The composite electrode material exhibited high specific capacitance of 293.5 F/g at the current density 1 A g−1 and also outstanding cyclic stability of 96% retained after 10,000 charge discharge (GCD) cycles at of 6 A g−1. The catalytic activity of ZnO sphere and ZnO sphere/r-GO composites shows the degradation percentage if 76.2 and 94.6%, respectively. ZnO sphere/r-GO composite shows around 24% of catalytic enhancement due to the high specific surface area of r-GO, and also the composite shows high reliability and degradation efficiency is still retained at 96.9% upto 5 cycles. The composite material is a potential candidate for high performance energy storage and photocatalytic applications.

In this work, we developed lab waste tissue paper derived activated carbon and bare Mn2P2O7/NF and polypyrrole (PPy) incorporated Mn2P2O7/NF@PPy materials by using hydrothermal and chemical polymerization methods. The phase confirmation, structural morphology, surface area information and chemical compositions of prepared materials were characterized by using XRD, FESEM, BET and XPS analysis. In electrochemical results of activated carbon, Mn2P2O7/NF and Mn2P2O7/NF@PPy electrodes capacitive and diffusive behaviours are discussed in this article. In effect of polypyrrole incorporated Mn2P2O7/NF@PPy electrode exhibits high specific capacitance of 658 Fg−1 at a current density of 1 Ag−1 compared with a bare electrode. The fabricated asymmetric device by using activated carbon as anode and Mn2P2O7/NF@PPy material as cathode material and delivers a high energy density of 27.4 Whkg−1 compared with recent developed activated carbon and polypyrrole based devices.

Identification of electrode materials with excellent specific capacity and energy density are significant factors for the development of high-performance supercapattery device. Transition metal tungstate is an emerging electroactive material for supercapattery due to its excellent electrical conductivity and electrochemical properties. Herein, the mesoporous Ni(1−x)Co(x)WO4 nanomaterials were synthesized by a one-step hydrothermal method as an anode material for supercapattery. The apparent discrepancy in mesoporous structures was incited by varying the stoichiometric ratio of Ni/Co in the Ni(1−x)Co(x)WO4 system which lead to an increase in the electrochemical properties. Among the synthesized electrode materials, Ni0.5Co0.5WO4 electrode material delivers the high specific capacity of 634.55 Cg−1 at 1 Ag−1 with an excellent rate capability of 92% after 10,000 cycles at 10 Ag−1. The solid-state supercapattery constructed with Nio.5Co0.5WO4 and reduced graphene oxide as positive and negative electrodes, respectively. The device exhibits the maximum specific capacity of 134.70 Cg−1 at 0.5 Ag−1 and energy density of 56.12 Wh kg−1 at 500 W kg−1 with long-term cyclic stability (90% capacity retentively after 20,000 cycles). The high performance of this electrode material has been attributed to the synergetic effect between bimetallic (Ni and Co) redox centers, a mesoporous structure that provides a larger redox cites, rich electrical conductivity, shorter diffusion length, and faster electrochemical kinetic rates for electrochemical reactions.

Author(s): Zhao, W; Kim, J; Huang, X; Zhang, L; Pesquera, D; Velarde, GAP; Gosavi, T; Lin, CC; Nikonov, DE; Li, H; Young, IA; Ramesh, R; Martin, LW | Abstract: The rapid development of computing applications demands novel low-energy consumption devices for information processing. Among various candidates, magnetoelectric heterostructures hold promise for meeting the required voltage and power goals. Here, a route to low-voltage control of magnetism in 30nnm Fe0.5Rh0.5/100nnm 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 (PMN-PT) heterostructures is demonstrated wherein the magnetoelectric coupling is achieved via strain-induced changes in the Fe0.5Rh0.5 mediated by voltages applied to the PMN-PT. We describe approaches to achieve high-quality, epitaxial growth of Fe0.5Rh0.5 on the PMN-PT films and, a methodology to probe and quantify magnetoelectric coupling in small thin-film devices via studies of the anomalous Hall effect. By comparing the spin-flop field change induced by temperature and external voltage, the magnetoelectric coupling coefficient is estimated to reach ≈7 × 10−8ns m−1 at 325 K while applying a −0.75nV bias.

The performances of the supercapacitor mainly rely on the design of electrode materials. The transition metal molybdates have been attracted as electrode material in supercapacitor due to their physicochemical properties. In the present work, a petal-like CoMoO4/r-GO composite was synthesized by a one-step hydrothermal method. The structural, morphological, and electrochemical properties were studied by using different analytical methods. As an electrode material, the CoMoO4/r-GO composite exhibited a high specific capacity of 425Cg-1at current density 1 Ag−1 with an excellent rate capability of 92.2% retained over 10,000 charge–discharge cycles at current density 10 Ag−1. Besides, the constructed asymmetric supercapacitor delivered a high energy density of 63.5 Wh kg−1 at a power density of 500 W kg−1.

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO3/SrTiO3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO3 and SrTiO3. Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics., Flexoelectric coupling between strain gradients and polarization influences the physics of ferroelectric devices but it is difficult to directly probe its effects. Here, Li et al. use principal component analysis to compare STEM images with phase-field modeling and extract the flexoelectric contributions.

A strain-driven orthorhombic (O) to rhombohedral (R) phase transition is reported in La-doped BiFeO3 thin films on silicon substrates. Biaxial compressive epitaxial strain is found to stabilize the rhombohedral phase at La concentrations beyond the morphotropic phase boundary (MPB). By tailoring the residual strain with film thickness, we demonstrate a mixed O/R phase structure consisting of O phase domains measuring tens of nanometers wide within a predominant R phase matrix. A combination of piezoresponse force microscopy (PFM), transmission electron microscopy (TEM), polarization–electric field hysteresis loop (P–E loop), and polarization maps reveal that the O-R structural change is an antiferroelectric to ferroelectric (AFE-FE) phase transition. Using scanning transmission electron microscopy (STEM), an atomically sharp O/R MPB is observed. Moreover, X-ray absorption spectra (XAS) and X-ray linear dichroism (XLD) measurements reveal a change in the antiferromagnetic axis orientation from out of plane...

Herein, sheet like WO3 nanostructures were synthesized by facile hydrothermal method in the presence and absence of urea. The phase formation and crystallinity of the synthesized samples were investigated by using powder X-ray diffraction technique, which revealed that the synthesized nanostructures in the presence of urea showed the high crystalline quality than the nanostructures synthesized in the absence of urea. Morphology and size of the synthesized nanostructures were identified from field-emission scanning electron microscope and transmission electron microscopy characterizations, which showed the sheet like morphology. The optical band gap was calculated as 2.57 and 3.03 eV for WO3 nanostructures synthesized in the presence and absence of urea respectively. Moreover, the photocurrent density was measured to study the photoelectrochemical water splitting performance of the synthesized nanostructures. The photocurrent density of 0.800 mA cm−1 at 1.2 V s. Ag/AgCl and 0.011 mA cm−1 at 1.2 V s. Ag/AgCl for WO3 nanostructures synthesized in the presence and absence of urea respectively. The higher photocurrent density of the WO3 nanostructures synthesized in the presence of urea was due to the improved charge transport property.

Electric-field-induced magnetic switching can lead to a new paradigm of ultra-low power nonvolatile magnetoelectric random access memory (MeRAM). To date the realization of MeRAM relies primarily on ferromagnetic (FM) based heterostructures which exhibit low voltage-controlled magnetic anisotropy (VCMA) efficiency. On the other hand, manipulation of magnetism in antiferromagnetic (AFM) based nanojunctions by purely electric field means (rather than E-field induced strain) remains unexplored thus far. Ab initio electronic structure calculations reveal that the VCMA of ultrathin FeRh/MgO bilayers exhibits distinct linear or nonlinear behavior across the AFM to FM metamagnetic transition depending on the Fe- or Rh-interface termination. We predict that the AFM Fe-terminated phase undergoes an E-field magnetization switching with large VCMA efficiency and a spin reorientation across the metamagnetic transition. In sharp contrast, while the Rh-terminated interface exhibits large out-of-plane (in-plane) MA in the FM (AFM) phase, its magnetization is more rigid to external E-field. These findings demonstrate that manipulation of the AFM Néel-order magnetization direction via purely E-field means can pave the way toward ultra-low energy AFM-based MeRAM devices.

Electric-field (E-field) control of magnetism enabled by multiferroic materials has the potential to revolutionize the landscape of present memory devices plagued with high energy dissipation. To date, this E-field controlled multiferroic scheme has only been demonstrated at room temperature using BiFeO3 films grown on DyScO3, a unique and expensive substrate, which gives rise to a particular ferroelectric domain pattern in BiFeO3. Here, we demonstrate reversible electric-field-induced switching of the magnetic state of the Co layer in Co/BiFeO3 (BFO) (001) thin film heterostructures fabricated on (001) SrTiO3 (STO) substrates. The angular dependence of the coercivity and the remanent magnetization of the Co layer indicates that its easy axis reversibly switches back and forth 45° between the (100) and the (110) crystallographic directions of STO as a result of alternating application of positive and negative voltage pulses between the patterned top Co electrode layer and the (001) SrRuO3 (SRO) layer on which the ferroelectric BFO is epitaxially grown. The coercivity (HC) of the Co layer exhibits a hysteretic behavior between two states as a function of voltage. A mechanism based on the intrinsic magnetoelectric coupling in multiferroic BFO involving projection of antiferromagnetic G-type domains is used to explain the observation. We have also measured the exact canting angle of the G-type domain in strained BFO films for the first time using neutron diffraction. These results suggest a pathway to integrating BFO-based devices on Si wafers for implementing low power consumption and nonvolatile magnetoelectronic devices.

The work is supported by U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award FG02-07ER46417 (L.-Q.C., F.X., and J.B.). Z.H. acknowledges the support by NSF-MRSEC Grant DMR-1420620 and NSF-MWN Grant DMR-1210588. A.R.D. acknowledges support from the Army Research Office under Grant W911NF-14-1-0104. L.W.M. acknowledges support from the National Science Foundation under Grant DMR-1451219. A.K.Y., C.T.N., and R.R. acknowledge support from the Office of Basic Energy Sciences, U.S. Department of Energy under contract no. DE-AC02-05CH11231. L.W.M. and R.R. acknowledge support from the Gordon and Betty Moore Foundation’s EPiQS Initiative, Grant GBMF5307. A novel mesoscale state comprising of an ordered polar vortex lattice has been demonstrated in ferroelectric superlattices of PbTiO3/SrTiO3. Here, we employ phase-field simulations, analytical theory, and experimental observations to evaluate thermodynamic conditions and geometric length scales that are critical for the formation of such exotic vortex states. We show that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper and a lower bound to the length scale at which these states can be observed. We found that the critical length is related to the intrinsic domain wall width, which could serve as a simple intuitive design rule for the discovery of novel ultrafine topological structures in ferroic systems. Postprint Postprint

Author(s): Ercius, Peter; Johnson, Ian; Brown, Hamish; Pelz, Philipp; Hsu, Shang-Lin; Draney, Brent; Fong, Erin; Goldschmidt, Azriel; Joseph, John; Lee, Jason; Ciston, Jim; Ophus, Colin; Scott, Mary; Selvarajan, Ashwin; Paul, David; Skinner, David; Hanwell, Marcus; Harris, Chris; Avery, Patrick; Stezelberger, Thorsten; Tindall, Craig; Ramesh, Ramamoorthy; Minor, Andrew; Denes, Peter

Nanoelectronic devices based on ferroelectric domain walls (DWs), such as memories, transistors, and rectifiers, have been demonstrated in recent years. Practical high-speed electronics, on the other hand, usually demand operation frequencies in the gigahertz (GHz) regime, where the effect of dipolar oscillation is important. Herein, an unexpected giant GHz conductivity on the order of 10

Ultrathin ferroelectric materials could potentially enable low-power logic and nonvolatile memories1,2. As ferroelectric materials are made thinner, however, the ferroelectricity is usually suppressed. Size effects in ferroelectrics have been thoroughly investigated in perovskite oxides—the archetypal ferroelectric system3. Perovskites, however, have so far proved unsuitable for thickness scaling and integration with modern semiconductor processes4. Here we report ferroelectricity in ultrathin doped hafnium oxide (HfO2), a fluorite-structure oxide grown by atomic layer deposition on silicon. We demonstrate the persistence of inversion symmetry breaking and spontaneous, switchable polarization down to a thickness of one nanometre. Our results indicate not only the absence of a ferroelectric critical thickness but also enhanced polar distortions as film thickness is reduced, unlike in perovskite ferroelectrics. This approach to enhancing ferroelectricity in ultrathin layers could provide a route towards polarization-driven memories and ferroelectric-based advanced transistors. This work shifts the search for the fundamental limits of ferroelectricity to simpler transition-metal oxide systems—that is, from perovskite-derived complex oxides to fluorite-structure binary oxides—in which ‘reverse’ size effects counterintuitively stabilize polar symmetry in the ultrathin regime. Enhanced switchable ferroelectric polarization is achieved in doped hafnium oxide films grown directly onto silicon using low-temperature atomic layer deposition, even at thicknesses of just one nanometre.

Uncompensated moments in antiferromagnets are responsible for exchange bias in antiferromagnet/ferromagnet heterostructures; however, they are difficult to directly detect because any signal they contribute is typically overwhelmed by the ferromagnetic layer. We use magneto-thermal microscopy to image uncompensated moments in thin films of FeRh, a room-temperature antiferromagnet that exhibits a 1st-order phase transition to a ferromagnetic state near 100~$^\circ$C. FeRh provides the unique opportunity to study both uncompensated moments in the antiferromagnetic phase and the interaction of uncompensated moments with emergent ferromagnetism within a relatively broad (10-15~$^\circ$C) temperature range near $T_C$. In the AF phase below $T_C$, we image both pinned UMs, which cause local vertical exchange bias, and unpinned UMs, which exhibit an enhanced coercive field that reflects exchange-coupling to the AF bulk. Near $T_C$, where AF and FM order coexist, we find that the emergent FM order is exchange-coupled to the bulk N\'eel order. This exchange coupling leads to the nucleation of unusual configurations in which different FM domains are pinned parallel, antiparallel, and perpendicular to the applied magnetic field before suddenly collapsing into a state uniformly parallel to the field., Comment: 29 pages and 16 figures with appendix

Author(s): Everhardt, AS; Dc, M; Huang, X; Sayed, S; Gosavi, TA; Tang, Y; Lin, CC; Manipatruni, S; Young, IA; Datta, S; Wang, JP; Ramesh, R | Abstract: Efficient charge to spin conversion is important for low-power spin logic devices. Spin and charge interconversion is commonly performed using heavy metals and topological insulators, while the field of oxides is not yet fully explored. Strontium iridate thin films were grown, where the different crystal structures form a perfect playground to understand the key factors in obtaining high charge to spin conversion efficiency (i.e., large spin Hall angle). It was found that the semiconducting Sr2IrO4 has a spin Hall angle of ∼0.1 (depending on measurement technique), which is promising for a spin-orbit coupled electronic system and comparable to Pt. In contrast, the perovskite SrIrO3, reported to have a Dirac cone near the Fermi level, has a larger spin Hall angle of 0.3-0.4 degrees. The largest difference between the two materials is a large degree of spin-momentum locking in SrIrO3, comparable to known topological insulators. A simple semiclassical relationship is found where the spin Hall angle increases for higher degrees of spin-momentum locking and it also increases for lower Fermi wave vectors. This relationship is then able to explain the decreased spin Hall angle below 10 nm film thickness in SrIrO3, by relating it to the correspondingly higher carrier concentration (related to the higher Fermi wave vector). Breaking the commonly believed anticorrelation between resistivity and carrier concentration paves a pathway to lower power losses due to resistance while keeping large spin Hall angles.

Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO3/SrTiO3 superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states. Upon ultrafast irradiation, a (PbTiO3)/(SrTiO3) superlattice transforms into a complex supercrystal that contains periodicities of up to 30 nm in size and is stable in ambient. Creation and destruction, by heating, of the supercrystal is reversible.

Negative capacitance is a newly discovered state of ferroelectric materials that holds promise for electronics applications by exploiting a region of thermodynamic space that is normally not accessible1–14. Although existing reports of negative capacitance substantiate the importance of this phenomenon, they have focused on its macroscale manifestation. These manifestations demonstrate possible uses of steady-state negative capacitance—for example, enhancing the capacitance of a ferroelectric–dielectric heterostructure4,7,14 or improving the subthreshold swing of a transistor8–12. Yet they constitute only indirect measurements of the local state of negative capacitance in which the ferroelectric resides. Spatial mapping of this phenomenon would help its understanding at a microscopic scale and also help to achieve optimal design of devices with potential technological applications. Here we demonstrate a direct measurement of steady-state negative capacitance in a ferroelectric–dielectric heterostructure. We use electron microscopy complemented by phase-field and first-principles-based (second-principles) simulations in SrTiO3/PbTiO3 superlattices to directly determine, with atomic resolution, the local regions in the ferroelectric material where a state of negative capacitance is stabilized. Simultaneous vector mapping of atomic displacements (related to a complex pattern in the polarization field), in conjunction with reconstruction of the local electric field, identify the negative capacitance regions as those with higher energy density and larger polarizability: the domain walls where the polarization is suppressed. Imaging steady-state negative capacitance in SrTiO3/PbTiO3 superlattices with atomic resolution provides solid microscale support for this phenomenon.

Using epitaxial stabilization, we synthesized single-phase (001)-oriented thin films of DyFe2O4+x on (111) MgAl2O4 substrates by molecular-beam epitaxy. The metastable DyFe2O4 polymorph formed is isostructural to known trigonal ferrimagnetic RFe2O4 phases with space group R3̄m, where R = Ho to Lu. The epitaxial DyFe2O4 thin films have two in-plane orientation relationships: [100] DyFe2O4 || 211̄ MgAl2O4 plus a twin variant related by a 60° in-plane rotation. DyFe2O4 is not bulk stable and has never been synthesized before. Indeed, it has been predicted to be on the edge energetically of what may be possible to stabilize. The fact that the RFe2O4 phase is stable for all elements leading up to dysprosium (Ho–Lu) leads us to believe that DyFe2O4 could be a “remnant metastable phase,” one which, given the right thermodynamic conditions, could become the lowest free energy phase. We find that although we are able to get structurally very close to R3̄m DyFe2O4, the films are not stoichiometric as they have an increased c lattice parameter, indicative of extra oxygen as is sometimes seen in other RFe2O4 phases. The unintended surplus oxygen opens questions regarding what may be achievable using such tricks as epitaxial stabilization to access metastable phases and whether this indeed constitutes “remnant metastability.”

The synthesis of fully epitaxial ferroelectric Hf0.5 Zr0.5 O2 (HZO) thin films through the use of a conducting pyrochlore oxide electrode that acts as a structural and chemical template is reported. Such pyrochlores, exemplified by Pb2 Ir2 O7 (PIO) and Bi2 Ru2 O7 (BRO), exhibit metallic conductivity with room-temperature resistivity of

Background: Leptin is an adipokine that has an important role in body weight regulation and endocrine function. Leptin also acts as a pro-inflammatory cytokine by inducing the production of Th1 cytokines. The aim of our study was to estimate the serum leptin levels in systemic lupus erythematosus (SLE) patients and analyze its associations with clinical manifestations of lupus and disease activity. Materials and Methods: This study was conducted on 80 patients who satisfied Systemic Lupus International Collaborating Clinics 2012 criteria for SLE and 40 healthy controls. Demographic, clinical, and laboratory parameters were recorded. SLE disease activity index (SLEDAI) was scored for all SLE patients. Serum leptin levels (ng/dl) were estimated by enzyme-linked immunosorbent assay and the results were analyzed by SPSS. Results: Baseline characteristics were comparable in both cases and controls. SLE patients had higher serum leptin levels as compared to controls (mean 16.01 vs. 5.86 ng/ml) which were statistically significant (P Conclusion: Patients with SLE had high serum leptin levels. High leptin levels were seen predominantly in mucocutaneous lupus and lupus nephritis. Serum leptin levels correlated positively with BMI and serum uric acid and negatively with serum HDL cholesterol levels but showed no correlation with disease activity markers.

The supercapacitors have been widely used in the field of electronics appliances and automobiles, but its utility is limited by low energy density and poor specific capacitance. Energy density and specific capacitance of the supercapacitor is invariably determined by the electrode materials. Herein, a novel 3D flower-like CuO/Co3O4/r-GO heterostructure was synthesized by the hydrothermal method and used as an anode material for high-performance supercapacitors in an alkaline electrolyte solution. The as-prepared 3D flower-like CuO/Co3O4/r-GO heterostructure with high surface area provides vast interfacial contact area between electrode and electrolyte solution which offers a fast surface reaction kinetics and improved conductivity, thereby the remarkable electrochemical performance is achieved. The prepared CuO/Co3O4/r-GO heterostructure material shows an ultra-high specific capacitance of 1458 Fg-1 at a current density of 0.5 Ag-1, exceptional rate capability, and stable long- term cycling performance (97% retention after 10000 successive charge-discharge cycles at 5 Ag-1). In as-assembled asymmetric supercapacitor, CuO/Co3O4/r-GO heterostructure is an anode material and r-GO is a cathode material. The assembled device shows a high specific capacitance of 198 Fg-1 at 2 Ag-1, an ultra-high power density of 10510.30 W kg−1, and a high energy density of 34.20 Wh kg−1. Meanwhile, the ASC device exhibits excellent rate capability (97%) after 10000 successive charge-discharge cycles at 5 Ag-1 in the PVA-KOH gel electrolyte.

Topological structures in ferroic materials have drawn great interest in recent years due to the richness of the underlying physics and the potential for applications in next generation electronics. Recent advances in atomically precise thin-film materials synthesis and characterization of structural/physical phenomena at unprecedented length/energy/time scales have enabled us to study exotic phases and their associated physics [Rößler et al., Nature 442, 797 (2006); S. Das, Nature 568, 368 (2019); Yadav et al., Nature 530, 198 (2016); and Stoica et al., Nat. Mater. 18, 377 (2019)]. It is appropriate that, in the second century of ferroelectrics, some dramatic discoveries are propelling the field into directions heretofore unimaginable. In this review, we explore the recent progress in ferroelectric-oxide superlattices in which researchers can control structure and physical properties through the application of epitaxial strain, layer thickness, temperature, electric field, etc. We provide a discussion of exotic topological structures (e.g., closure domains, vortices, polar skyrmions, and other exotic phases) and associated functionalities in ferroelectric/paraelectric superlattices. We conclude with a brief overview of and prospects for how the field may evolve in the coming years.

A single-phase multiferroic material is constructed, in which ferroelectricity and strong magnetic ordering are coupled near room temperature, enabling direct electric-field control of magnetism. Materials that exhibit coupled ferroelectric and magnetic ordering are attractive candidates for use in future memory devices, but such materials are rare and typically exhibit their desirable properties only at low temperatures. Julia Mundy and colleagues now describe and successfully implement a strategy for building artificial layered materials in which ferroelectricity and magnetism are both present, and coupled near room temperature. Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism1,2. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism3. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms4,5,6,7,8,9,10,11,12,13,14,15, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications2. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling16—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially—from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

Multifunctional, complex oxides capable of exhibiting highly-coupled electrical, mechanical, thermal, and magnetic susceptibilities have been pursued to address a range of salient technological challenges. Today, efforts are focused on addressing the pressing needs of a range of applications and identifying, understanding, and controlling materials with the potential for enhanced or novel responses. In this prospective, we highlight important developments in theoretical and computational techniques, materials synthesis, and characterization techniques. We explore how these new approaches could revolutionize our ability to discover, probe, and engineer these materials and provide a context for new arenas where these materials might make an impact.

Significance Interfaces of transition-metal oxides (TMOs) offer a fertile platform to uncover emergent states, which has been extensively explored in 3 d TMOs with strong electron correlations. Recently research on 5 d TMOs with pronounced spin–orbit coupling (SOC) is flourishing due to the emergence of new topological states and potential application in spintronics. Interfaces between 3 d and 5 d TMOs provide a unique test bed to combine the merits of these two fundamental interactions. However, so far research is limited. Here we present results on one model system comprising the ferromagnet La 2/3 Sr 1/3 MnO 3 and the strong SOC paramagnet SrIrO 3 . We observe a manipulation of the magnetic anisotropy by tuning the SrIrO 3 dimensionality, which is accompanied by a novel SOC state in SrIrO 3 .

Ferroelectrically driven nonvolatile memory is demonstrated by interfacing 2D semiconductors and ferroelectric thin films, exhibiting superior memory performance comparable to existing thin-film ferroelectric field-effect transistors. An optical memory effect is also observed with large modulation of photoluminescence tuned by the ferroelectric gating, potentially finding applications in optoelectronics and valleytronics.

We report subthreshold swings as low as 8.5 mV/decade over as high as eight orders of magnitude of drain current in short-channel negative capacitance FinFETs (NC-FinFETs) with gate length $L_{g}=100$ nm. NC-FinFETs are constructed by connecting a high-quality epitaxial bismuth ferrite (BiFeO3) ferroelectric capacitor to the gate terminal of both n-type and p-type FinFETs. We show that a self-consistent simulation scheme based on Berkeley SPICE Insulated-Gate-FET Model:Common Multi Gate model and Landau–Devonshire formalism could quantitatively match the experimental NC-FinFET transfer characteristics. This also allows a general procedure to extract the effective $S$ -shaped ferroelectric charge–voltage characteristics that provides important insights into the device operation.

This work describes the preparation of hematite photoanode with suppressed both bulk and surface charge recombination rates by combined hydrothermal synthesis and hybrid microwave annealing (HMA) process. Three-dimensional branches like morphology were obtained for HMA processed photoanoanode. The obtained HMA processed photoanode shows enhanced PEC performance as compared with photoanode treated by a conventional annealing process with a photocurrent density of 0.32 mAcm−2 at 1.23 V vs RHE. Optical absorbance, electrochemical impedance spectroscopy, Mott-Schottky and hole scavenger oxidation measurements were demonstrated that the suppresses charge carriers recombination rates in bulk and surface state of hematite photoanode and enhances the donor density, thereby the PEC water splitting performance was enhanced. The enhanced PEC water splitting performance HMA processed hematite could be attributed to well define branches like morphology with high crystallinity and increased optical absorption.