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A novel -SCO was formed from the BM-SCO parent material by Cu-substitution. Although the oxygen content was lowered, the electric conductivity improved by 2–3 orders of magnitude, and the OER performances were greatly improved.

The half-metallic manganite oxide La

In this work, we report the resistive switching behavior of an amorphous La2Ti2O7 (LTO) film as sandwiched between two Pt electrodes. The resistive switching is forming-free and highly uniform. Furthermore, it exhibits self-rectifying resistive switching behaviors owing to the Schottky contact and quasi-ohmic contact formed at the top and bottom interfaces, respectively. The mechanism of switching behavior in the device is attributed to the trapping/detrapping-mediated electronic bipolar resistance switching. By fitting the current-voltage characteristics, it indicates the coexistent conduction mechanisms of Schottky emission and space-charge-limited-conduction (SCLC), while the Schottky barrier modified by electron trapping/detrapping plays a dominating role in the resistive switching process.

CuInP2S6 with robust room-temperature ferroelectricity has recently attracted much attention due to the spatial instability of its Cu cations and the van der Waals (vdW) layered structure. Herein, we report a significant enhancement of its remanent polarization by more than 50% from 4.06 to 6.36 µC cm− 2 under a small pressure between 0.26 to 1.40 GPa. Comprehensive analysis suggests that even though the hydrostatic pressure suppresses the crystal distortion, it initially forces Cu cations to largely occupy the interlayer site, causing the spontaneous polarization to increase. Under intermediate pressure, the condensation of Cu cations to the ground state and the polarization increase due cell volume reduction compensate each other, resulting in a constant polarization. Under high pressure, the migration of Cu cations to the center of the S octahedron dominates. These findings improve our understanding of this fascinating vdW ferroelectric material, and suggest new ways to improve its properties.

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO3/BiMnO3 SLs with considerable ferroelectric polarizations and tunable magnetic moments. The polarization of BiFeO3/BiMnO3 SLs presents a decent value of 12 μC/cm2, even as the dimensionality of BiFeO3 layers per period is reduced to about five-unit cells when keeping the BiMnO3 layers same. Moreover, it is found that the tunable magnetic moments of SLs are linked intimately to the dimensionality of BiFeO3 layers. Our simulations demonstrate that the superexchange interaction of Fe-O-Mn tends to be antiferromagnetic (AFM) with a lower magnetic domain formation energy rather than ferromagnetic (FM). Therefore, as the dimensionality of BiFeO3 per period is reduced, the AFM superexchange interaction between BiFeO3 and BiMnO3 in the SLs becomes weak, promoting a robust magnetization. This interlayer modulation effect in SLs presents an alluring way to accurately control the multiple order parameters in a multiferroic oxide system.

Introduction: Stress during adolescence causes long-term behavioral changes in adulthood. We previously found that adolescent exposure to predatory risk augments adolescent social contact and adult parental behavior in Brandt’s voles (Lasiopodomys brandtii). Methods: Here, we determined whether this experience alters sexual behavior, pair-bond formation, and recognition ability as well as basal HPA axis activity, central oxytocin (OT), and arginine-vasopressin (AVP) expression in adulthood. Results: In the social interaction test, repeated cat odor (CO) exposure enhanced the frequency of lordosis by female voles toward an unfamiliar opposite-sex conspecific. CO voles preferred to engage with their partners after 48-h cohabitation whereas the control groups did not, which may reflect stable pair bonds in the CO treatment group. Furthermore, adolescent exposure to CO inhibited novel object recognition and place recognition ability, while it influenced social recognition only among adult males. No effect of adolescent CO exposure was observed for basal HPA axis activity, showing a habituation effect. Finally, we found that CO exposure increased OT and decreased AVP expression in the hypothalamus, including the paraventricular nucleus and anterior hypothalamus. The levels of OT in the medial amygdala were lower, and AVP in the lateral septum was higher in CO voles compared with the control. Conclusion: These findings demonstrate that adolescent exposure to predator risk promotes adult reproductive behavior of Brandt’s voles. Deficits in recognition ability may necessitate alterations in reproductive strategies to enhance inclusive fitness. OT and AVP systems may play a modulatory role in the alteration of social behaviors elicited by adolescent predatory risk.

Multiferroic materials with multifunctional characteristics play a critical role in the field of microelectronics. In a perovskite oxide, ferroelectric polarization and ferromagnetism usually cannot coexist in a single-phase material at the same time. In this work, we design a superlattice structure composed of alternating BiFeO3 and BiMnO3 layers and illustrate how tuning the supercell size of epitaxial BiFeO3/BiMnO3 superlattices facilitates ferroelectric polarization while maintaining relatively strong ferromagnetism. A comprehensive investigation reveals that the enhanced ferroelectric polarization of BiMnO3 layers originates from the induction effect induced by a strong polarization field generated by the adjacent ferroelectric BiFeO3 layers. For the magnetic behavior, we consider the existence of interfacial antiferromagnetic superexchange interaction of Fe-O-Mn between BiFeO3 and BiMnO3 layers in our superlattices. This modulation effect of artificial superlattices provides a platform to accurately control the multiple order parameters in a multiferroic oxide system.

Multiferroic materials with flexibility are expected to make great contributions to flexible electronic applications, such as sensors, memories, and wearable devices. In this work, super‐flexible freestanding BiMnO3 membranes with simultaneous ferroelectricity and ferromagnetism are synthesized using water‐soluble Sr3Al2O6 as the sacrificial buffer layer. The super‐flexibility of BiMnO3 membranes is demonstrated by undergoing an ≈180° folding during an in situ bending test, which is consistent with the results of first‐principles calculations. The piezoelectric signal under a bending radius of ≈500 µm confirms the stable existence of electric polarization in freestanding BiMnO3 membranes. Moreover, the stable ferromagnetism of freestanding BiMnO3 membranes is demonstrated after 100 times bending cycles with a bending radius of ≈2 mm. 5.1% uniaxial tensile strain is achieved in freestanding BiMnO3 membranes, and the piezoresponse force microscopy (PFM) phase retention behaviors confirm that the ferroelectricity of membranes can survive stably up to the strain of 1.7%. These super‐flexible membranes with stable ferroelectricity and ferromagnetism pave ways to the realizations of multifunctional flexible electronics., As flexible device have become vital in the forefront of technology, the maintenance of multifunctional performances under high flexion is highly desired. Here, the synthesis of super‐flexible freestanding BiMnO3 membranes with stable ferroelectricity and ferromagnetism simultaneously by pulsed laser deposition using recently promising water‐soluble Sr3Al2O6 as the sacrificial layer is reported.

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO

Complex oxides with tunable structures have many fascinating properties, though high-quality complex oxide epitaxy with precisely controlled composition is still out of reach. Here we have successfully developed solution-based single-crystalline epitaxy for multiferroic (1-x)BiTi(1-y)/2FeyMg(1-y)/2O3–(x)CaTiO3 (BTFM–CTO) solid solution in large area, confirming its ferroelectricity at the atomic scale with strong spontaneous polarization. Careful compositional tuning leads to a bulk magnetization of 0.07 ± 0.035 μB/Fe at room temperature, enabling magnetically induced polarization switching exhibiting a large magnetoelectric coefficient of 2.7–3.0 × 10−7 s/m. This work demonstrates the great potential of solution processing in large-scale complex oxide epitaxy and establishes novel room-temperature magnetoelectric coupling in epitaxial BTFM–CTO film, making it possible to explore a much wider space of composition, phase, and structure that can be easily scaled up for industrial applications.

Oxygen nonstoichiometry plays a critical role in determining the physical and chemical functionalities of oxide materials. For widespread applications involving oxygen transport and exchange with t...

All perovskite p-i-n junction La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3/La0.7Te0.3MnO3 heterostructures were epitaxially deposited on (0 0 1) SrTiO3 substrates. Crystallinities and strain were investigated for p-i-n junction layers. The heterostructures show excellent ferroelectric and switchable domain structures. With the rising temperature, the junctions exhibit a transition from a p-i-n junction (hole/electron) with remarkable diode effect to a p-i-p like junction (hole/small polaron) with a small rectification. The temperature-dependent rectification of p-i-n junctions with 10 nm PZT layer show the consistent trend with that of junctions with 20 nm PZT layer. Our result indicated that the p-i-n junction may provide potential for further research and application.

Currently, although some progress has already been achieved, the complex and high-cost synthetic route, and low electrochemical properties of supercapacitor still restrict its practical application. Here, NiMoO4/NiO nanoflowers material with a high specific surface area grown on a nickel foam conductive substrate is successfully synthesized via a facile and efficient method, which exhibits an excellent capacitance of 10.3 F cm−2 (1982.3 F g−1), a good rate capability, and a remarkable cycling stability (capacity remain 98.6% after 3000 cycles). In addition, a novel asymmetric supercapacitor with excellent energy density is also fabricated via the NiMoO4/NiO nanoflowers as the positive electrode and a piece of active carbon as the negative electrode in 3 M KOH electrolyte. The optimized asymmetric device operating at 1.7 V also offers a high energy density and an outstanding long-term cycling stability. These impressive results suggest that such NiMoO4/NiO nanoflowers can pave the way for designing and developing next-generation high-performance storage systems.

The heterostructures based on multiferroic BiFeO3 (BFO) have received much attention for the great potential in magnetoelectric coupling and spintronic applications. Therefore, the BFO films combined with rhombohedral (R) phase and tetragonal (T) phase can bring in various functionalities. Here, we demonstrate that the Ta/Pt/Co/Pt multilayers grown on R-, T-, and mixed-phase BFO exhibit perpendicular magnetic anisotropy. We find that the magnetic switching behavior of the multilayer is sensitive to the phase of the BFO layer. The Ta/Pt/Co/Pt layers grown on top of the pure R- or T-phase BFO show one-step anomalous Hall effect (AHE) switching. However, the layers grown on the mixed-phase BFO show steplike AHE switching. We attribute that the steplike switching behavior originates from the two different interfacial situations between mixed-phase BFO and above layers. Our results bring a potential avenue for realizing spintronic devices based on mixed-phased BFO.

The spin Hall magnetoresistance (SMR) at Pt/ Y3Fe5O12(YIG) interfaces with (100)-, (110)- and (111)-oriented YIG films was studied. Before that, high-quality YIG films were fabricated on Gd3Ga5O12 (GGG) substrates by pulsed-laser deposition and the structure, magnetic property and damping of YIG films with different crystallographic orientations were compared and analyzed. By angle-dependent magnetoresistance (ADMR) measurements in neighboring Pt layer of YIG films, an anisotropy of SMR was observed. The spin mixing conductance (SMC) at different Pt/YIG interfaces was calculated according to the model of SMR. It was found that Pt/YIG (100) and Pt/YIG(110) interfaces have larger SMC than that of Pt/YIG(111) interface due to the relatively larger surface roughness, which could provide a reference for optimizing the performance of magnetic transport property in magnonic devices involving Pt/YIG interface.

Large data storage at reduced dimension is of a great deal of interest in spintronic devices in which magnetic oxide films lead for realizing the modulation of perpendicular magnetic anisotropy (PMA). Herein, we report the modulation of PMA in oxide heterostructures composed of one manganite layer sandwiched between two cobaltite layers, i.e., LaCoO3− δ/La0.7Sr0.3MnO3/LaCoO3− δ via oxygen vacancies. The PMA is originated by the orbital reconstruction and ferromagnetic exchange interaction at the interface between the CoO6 and MnO6 octahedra layers. The modulation ratio up to a significant value ∼200% of PMA can be realized through the phase transition of LaCoO3− δ layers between perovskite and brownmillerite via deprivation or replenishment of oxygen sites. The antiferromagnetic superexchange interaction at the interface between the oxygen-deficient CoO4 tetrahedra layer and the adjacent MnO6 octahedral layer with lattice distortion may suppress the magnetization and PMA. This work ensures promising outcomes in situ modulation of PMA in oxide films such as ferroelectric polarization or ionic liquid gating via the transport of oxygen vacancies.

Multiferroic materials with multifunctional characteristics play a critical role in the field of microelectronics. In a perovskite oxide, ferroelectric polarization and ferromagnetism usually cannot coexist in a single-phase material at the same time. In this work, we design a superlattice structure composed of alternating BiFeO

The strain effect on charge transfer in correlated oxide La0.8Sr0.2MnO3/NdNiO3 (LSMO/NNO) heterostructures is investigated. This is achieved by carefully tailoring the strain on the two layers using various substrates. In contrast to bare LSMO films, the strain dependence of the enhanced magnetic moment of the LSMO/NNO bilayers strongly suggests that the charge transfer can be controlled via strain engineering in complex oxide heterostructures. Furthermore, our study also reveals that the coercive field, exchange bias, and conductivity are dramatically affected by the strain-modulated charge transfer in LSMO/NNO heterostructures. Our work thus points out a new path to control electronic states in oxide heterostructures to advance the use of interfaces in oxide-based electronics.

It is still a huge challenge to obtain a high-energy-density asymmetric supercapacitors and develop an active electrode material with excellent electrochemical characteristics. Although NiCo 2 S 4 has been considered as one of the promising positive electrode materials for asymmetric supercapacitors, the electrochemical performance of the NiCo 2 S 4 -based positive electrodes is still relatively low and cannot meet the demand in the devices. Herein, NiCo 2 S 4 /Co 9 S 8 nanorods with a large capacitance are synthesized via a simple two-step hydrothermal treatment. A high-performance asymmetric supercapacitor operating at 1.6 V is successfully assembled using the NiCo 2 S 4 /Co 9 S 8 nanorods as positive electrode and activated carbon as negative electrode in 3 M KOH aqueous electrolyte, which demonstrates a fairly high energy density of 49.6 Wh kg −1 at a power density of 123 W kg −1 , an excellent capacitance of 0.91 F cm −2 (139.42 F g −1 ) at current density of 1 mA cm −2 as well as a remarkable cycling stability due to the high physical strength, the large specific surface area, and the good conductivity for NiCo 2 S 4 /Co 9 S 8 nanorods and the brilliant synergistic effect for NiCo 2 S 4 and Co 9 S 8 electrode materials. The as-prepared NiCo 2 S 4 /Co 9 S 8 nanorods open up a new platform as positive electrode material for high-energy-density asymmetric supercapacitors in energy-storage.

In this work, a high-performance asymmetric supercapacitor device based on NiCo 2 S 4 /NiS hollow nanospheres as the positive electrode and the porous activated carbon as the negative electrode was successfully fabricated via a facile two-step hydrothermal synthesis approach. This NiCo 2 S 4 /NiS//activated carbon asymmetric supercapacitor achieved a high energy density of 43.7 Wh kg −1 at a power density of 160 W kg −1 , an encouraging specific capacitance of 123 F g −1 at a current density of 1 mA cm −2 , as well as a long-term performance with capacitance degradation of 5.2% after 3000 consecutive cycles at 1 mA cm −2 . Moreover, the NiCo 2 S 4 /NiS electrode also demonstrated an excellent specific capacitance (1947.5 F g −1 at 3 mA cm −2 ) and an outstanding cycling stability (retaining 90.3% after 1000 cycles). The remarkable electrochemical performances may be attributed to the effect of NiS doping on NiCo 2 S 4 which could enlarge the surface area and increase the surface roughness.

CoMoO 4 /Co 9 S 8 nanorod arrays supported on nickel foam are successfully assembled via a facile two-step hydrothermal route. Due to the unique nanorod array structure, the CoMoO 4 /Co 9 S 8 , as the electrode, possesses a high capacity 1.54 mA h·cm −2 (343.21 mA h·g −1 ) and a large capacitance 9.17 F cm −2 (2059.26 F g −1 ) at a current density of 20 mA·cm −2 (4.44 A·g −1 ), and an excellent cycling stability (8.6% degradation after 3000 cycles). The asymmetric supercapacitor based on the CoMoO 4 /Co 9 S 8 nanorod arrays as a positive electrode and porous active carbon as a negative electrode in an alkaline KOH aqueous electrolyte is fabricated. Owing to the synergetic effect between CoMoO 4 /Co 9 S 8 and active carbon, CoMoO 4 /Co 9 S 8 //active carbon asymmetric supercapacitor exhibits an outstanding energy density of 42 Wh·kg −1 and an excellent cycling stability with 89.5% specific capacitance retained after 5000 cycles in an operating voltage of 1.6 V. The facile synthesis route and remarkable supercapacitive performance of the CoMoO 4 /Co 9 S 8 nanorod arrays is promising as a positive electrode materials for high-performance asymmetric supercapacitors.

Exchange bias lies in the core of cutting-edge technologies, for instance, high-density data storage, spin valves, and high-frequency magnetic devices. As the devices with flexibility have become vital in the forefront of technology, the maintenance of exchange bias under high flexion is highly desired. This paper reports the strong exchange bias in flexible freestanding La0.7Sr0.3MnO3/BiFeO3 membranes with decent mechanical durability. The La0.7Sr0.3MnO3 layer is biased strongly by the BiFeO3 layer even in the freestanding state. At the same time, the strain is demonstrated to affect the strength of the exchange bias of the La0.7Sr0.3MnO3/BiFeO3 bilayer. Furthermore, the saturation magnetization and exchange bias field of the freestanding La0.7Sr0.3MnO3/BiFeO3 membranes are preserved well after 1000 bending cycles. Our work on freestanding membranes paves the way for manufacturing advanced flexible spintronic devices.

The evidence for a spin-lattice coupling in a tetragonal-like BiFeO3 (BFO) film is derived from thermal expansion measurements. Taking the advantage of La doping, the Neel temperature (TN) of the BFO film can be further adjusted over a broad range of temperatures. The lattice parameters exhibit anomalies near the Neel temperatures. The Bi0.8La0.2FeO3 film has a spin order-to-disorder transition at the TN without a structural phase transition, suggesting that a spin-lattice coupling drives the thermal expansion anomalies. The spin-lattice coupling can be enhanced by the coexistence of phases in the thicker BFO films. The density functional theory calculations show a smaller lattice constant of the c axis in the spin-order state than that in the spin-disorder state for the same tetragonal-like phase, which supports that the thermal expansion anomalies are a consequence of the spin-lattice coupling. Our findings may have application prospects for functional materials with controllable thermal expansions.

CoW films with different compositions have been prepared by an electrochemical deposition method. The tungsten contents in the CoW films are controlled by adjusting electrolyte concentrations, pH values, and applied potentials. The magnetic and corrosion-resistant properties of the CoW films are systematically studied. With an increase in tungsten content and annealing temperature, the CoW films shift from in-plane magnetic anisotropy to magnetic isotropy, which is due to the formation of a hexagonal close packed (hcp) Co3W phase confirmed by morphological and phase evolutions. The magnetic properties of the CoW films remain stable even after immersion in a 0.5% NaCl solution for 170 hours. An ultrathin tungsten oxide passivation layer coated on the surface of the films protects the CoW films from corrosion.

We have prepared CoPt/Ag core/shell nanoparticles (NPs) by the seed-medium method and demonstrated that Ag shells perform a crucial role in the magnetic enhancement of CoPt NPs. The NPs were annealed under Ar+5%H 2 atmosphere at different temperatures and the coercivities of both CoPt and CoPt/Ag NPs increase with the rise of annealing temperature. The room temperature coercivity of the CoPt/Ag NPs reaches 19 kOe after annealing at 650 °C, which is much higher than that of CoPt NPs (∼2880 Oe). From XRD patterns, the (001) and (110) peaks of the CoPt/Ag NPs are stronger than those of the CoPt ones, indicating a more complete L 1 0 phase transition induced by Ag shells.

Magnetism control has a variety of applications in magnetic storage and spintronic devices. Instead of the control of direct magnetoelectric coupling via strain, voltage, and Dzyaloshinskii-Moriya interaction, the polarization-dependent coupling in multiferroic materials such as BiFeO3 is employed for the electric-field control of magnetizations in this work. A perpendicular magnetic anisotropy (PMA) has been realized in a BiFeO3/Al2O3/Pt/Co/Pt multiferroic structure at room temperature. Interestingly, a distinct change of coercivity field (∼400%) has been observed in the structure with opposite polarization directions, which can be attributed to the different oxidation degree at the Pt/Co interface. This spontaneous polarization-controlled switching not only provides us a platform to study the interfacial effect in multiferroic heterostructures but also paves the way to manipulate PMA or even spin orbit torque through oxygen vacancies.

A novel resistive random access memory device is designed with SrTiO3/ La2/3Sr1/3MnO3 (LSMO)/MgAl2O4 (MAO)/Cu structure, in which metallic epitaxial LSMO is employed as the bottom electrode rather than traditional metal materials. In this device, the critical external compliance current is no longer necessary due to the high self-resistance of LSMO. The LMSO bottom electrode can act as a series resistor to offer a compliance current during the set process. Besides, the device also has excellent switching features which are originated in the formation of Cu filaments under external voltage. Therefore it provides the possibility of reducing power consumption and accelerating the commercialization of resistive switching devices.

Organic and polymer-based resistive memory cell sandwiched between two vertically aligned electrodes constitute crossbar memory arrays in which the building blocks, referred to as bit cells, possess two or multiple stable resistance states.1 They are promising circuit elements due to their good scalability and processability, high possibility of molecular design through chemical synthesis, high storage density, amenability to processing onto a variety of substrates, large-area and low-cost deposition techniques such as spin coating, roll-to-roll processing, ink jet printing, and electrochemical processing.2 Additionally, the polymer also presents other favorable properties working as special electronic devices, such as excellent mechanical strengths, lightweight and flexibility.3 In this paper, the resistive switching feature of the electromagnetic PPy composite films with magnetic metal cobalt nanoparticles (Co NPs) is investigated for the first time. The pure PPy film does not show any resistive switching phenomenon, while the Co-PPy composite films show obvious bipolar resistive switching with a typical filamentary feature. The role of the Co NPs for resistive switching in the Co-PPy composite films and the detailed mechanism are discussed.

The resistive switching behavior of Co-nanoparticle-dispersed polypyrrole (PPy) composite films is studied. A novel design method for resistive random access memory (ReRAM) is proposed. The conducting polymer films with metal nanocrystal (NC)-dispersed carbon chains induce the spontaneous oxidization of the conducting polymer at the surface. The resistive switching behavior is achieved by an electric field controlling the oxygen ion mobility between the metal electrode and the conducting polymer film to realize the mutual transition between intrinsic conduction (low resistive state) and oxidized layer conduction (high resistive state). Furthermore, the formation process of intrinsic conductive paths can be effectively controlled in the conducting polymer ReRAM using metal NCs in films because the inner metal NCs induce electric field lines converging around them and the intensity of the electric field at the tip of NCs can greatly exceed that of the other region. Metal NCs can also bring new characteristics for ReRAM, such as magnetism by dispersing magnetic metal NCs in polymer, to obtain multifunctional electronic devices or meet some special purpose in future applications. Our works will enrich the application fields of the electromagnetic PPy composite films and present a novel material for ReRAM devices.

The effect of oxide/oxide interface for controlling the migration process of oxygen vacancies (or oxygen ions) on resistive switching behaviors has been investigated by fabricating the ZrO2/ZnO oxide heterostructures. Completely different resistive switching behaviors are observed in the heterostructures with a set process under a different bias polarity. It is demonstrated that the change of the oxide/oxide interface barrier height determining the migration of oxygen vacancies (or oxygen ions) leads to the current direction-dependent resistive switching. Furthermore, the ZnO/ZrO2 heterostructure with the homogeneous resistive switching behavior could be potentially applied as a controllable and stable multistate memory by controlling reset-stop voltages. Our method opens up an opportunity to explore the resistive switching mechanism and develop resistance switching devices with specific functions through engineering oxide/oxide interfaces in oxide heterostructures.