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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.

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.

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 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.

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.

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.

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.