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Via exploring the spin dynamics and transport properties at interfaces of magnetic material/non-magnetic metal bilayers, spintronics advanced many techniques on generation, detection, and manipulation of spin currents, which laid down a foundation for designing spintronic devices. New ideas and methods for manipulating spin are required in the spintronics community. Merging with cavity quantum electrodynamics, magnetic resonance in ferromagnets inside of a microwave cavity, realizes a strong magnon-microwave coupling at room temperature, opening an avenue to manipulate spin and spin current for the spintronics community. Spin-microwave coupling strength was significantly improved by replacing a few spins in a paramagnetic spin system with magnetization in ferromagnetic materials. Thus, a strongly coupled magnon-microwave system offers a hybrid quantum platform with many measures to tune the coupled system, such as an exchange magnetic field, an anisotropy field, controlled coupling strength, controlled damping parameters, and so on. Many devices were proposed and demonstrated with potential applications. In this review, we briefly introduce the concept and mechanism of magnon-microwave coupling, a classical electrodynamical coupling model for the coupling, spin currents produced by the coupled magnon, and manipulation of the spin current via the strong coupling. In ferromagnets, magnons can couple to a microwave mode as a magnon-polariton propagating in the materials. The strongly coupled magnon-microwave system is a magnon-polariton in a cavity where the microwave was confined as a resonance mode with a high quality factor. Using the Landau-Lifshitz-Gilbert equation and Maxwell equations, we introduce the classical electrodynamical coupling model and reveal that the magnon is driven by a torque produced by the microwave magnetic field on the magnetization and the microwave is feedback via Faraday’s law. Therefore, the coupling strength of the magnon-microwave system can be controlled by changing the torque. Magnon-microwave coupling is experimentally studied using many techniques, such as microwave transmission, Brillouin light scattering, Faraday rotation measurement, and spin pumping electrical detection. Spin pumping is well explored in the spintronics community as a spin current produced by magnon and detected as a voltage via inverse spin Hall effect in a novel metal. Combining with microwave transmission of the coupled microwave subsystem, spin pumping electrical detection by directly detecting the spin current produced by the magnon subsystem in the coupled system, illustrates a more complete profile of the coupled magnon-microwave system. In addition, the strongly coupled magnon-microwave system offers a new technique to manipulate spin currents. We experimentally demonstrate that spin currents produced by the strongly coupled system are correlated with each other mediated by the microwave cavity, and can be manipulated remotely. Two almost identical magnet samples are used to couple to a cavity and the coupling strengths between each magnet and the cavity are tunable individually. By using electrical detection to locally detect each magnet sample respectively, we find that the spin currents produced by two magnet samples are coherently correlated. By tuning the coupling strength of one magnet sample to the cavity, the spin current produced by the second magnet sample is manipulated distantly over a few centimeters, which is far longer than the distance of spin-orbit interaction or exchange interaction. This distant control is only limited by the coherence length of the microwave and the dimension of the cavity. This flexibility opens the door to improve spin current generation and manipulation for cavity spintronic devices.

Low-dimensional materials have been drawing increasing interest due to the unique structures and fascinating properties which are quite promising for wide-range application ranging from new energy resources to information technology. The exotic electronic states of the low-dimensional materials which arise from the quantum-confinement effects of electrons render a potential strategy to overcome the size-limitation of traditional semiconducting materials and continue the Moores’ law which is difficult for the conventional bulk materials. The electronic structure modulation of low-dimensional materials to meet the relevant requirements serves as the key to reach this goal. Notably, in low-dimensional materials, the defect effects are more remarkable than those in bulk materials due to the high specific surface area and quantum confinement effects. Moreover, the compatibility of low-dimensional materials to nanoscaled devices is crucial for the next-generation device applications. Here, we focus on the role of defects in electronic structure modulation of one- (1D) and two-dimensional (2D) materials to summarize works of our group relevant to this topic in recent years. The point defects, such as vacancies and adatoms (or functional groups) are revealed to have significant contribution to the electron spin-polarization and excited states. The ferromagnetism of the metal-free materials is demonstrated in wide range of materials, such as graphite, hexagonal boron nitride and silicon carbide both theoretically and experimentally. The spin-polarization of p electrons in these materials enriches the family of ferromagnetic materials and offers a promising strategy for spintronics device applications. The hollow structure of carbon nanotubes provides an ideal platform for the study of atomic reaction, diffusion and condensation processes confined in nanospace. The electronic band structures of carbon nanotubes can be effectively regulated by encapsulating metal or hydrogen nanowires. Ultrahigh density of hydrogen nanowires can be confined inside carbon nanotubes, thanks to the excellent mechanical properties, which lead to metallization or superconductivity of the 1D hydrogen systems at relative low pressure and high temperature, due to the “physical compression” effect of carbon nanotubes. The superconducting hydrogen can be well explained in terms of the Eliashberg superconductivity theory for electron-phonon strong-coupling system. The metallization and superconducting phase of hydrogen nanowires encapsulated in carbon nanotubes open a promising platform for study of low-dimensional superconductivity at high pressure. Additionally, metal-organic frameworks (MOFs) which are composed of transition metal (TM) atoms and organic ligands emerged as a new family of 2D materials. Compared with traditional 2D materials, MOFs have the advantages of structural diversity, porous configurations, tunable electronic band structures. Some lattice models, such as Kagome, Lieb and Ruby lattice models can be achieved in 2D MOFs. The synergistic effect of TM atoms and organic ligands leads to exotic properties, such as Kane fermions, topological electronic states (quantum spin Hall effects and quantum anomalous Hall effect), superconductivity, high catalytic activity, etc. The well-distributed TM atoms in the porous structures of 2D MOFs facilitate the catalysis in hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which hold great promise in water splitting and fuel cells. In view of the experimental progresses on the synthesis of diverse 2D MOFs, the fascinating properties of 2D MOFs bring about new concepts for electronic devices and catalysis design.

Novel spintronic devices with low power consumption, nonvolatility, and high storage density are highly desired to meet the rapid development of modern information storage and communication technology, which poses a great challenge to both material and device researches. To overcome this challenge, our group has focused our research on the following two aspects. On one hand, we have explored novel magnetoresistance effects in a variety of materials and devices, aiming to get a deep understanding about the spin dependent transport and obtain an effective control of spin-dependent transport. On the other hand, we have tried to control the magnetoresistance based on multi-physical field effects, aiming to obtain spintronic prototype devices that can be used for multi-state data storage. Regarding the novel magnetoresistance explorations, this article will introduce: (1) The negative magnetoresistance in amorphous condensed magnetic semiconductors. The spin dependent variable range hopping model is proposed, which can quantitatively explain the temperature and magnetic field dependent transport behavior in the condensed magnetic semiconductors. In addition, this model provides an alternative way to detect the spin polarization ratio of the magnetic semiconductors. (2) The positive magnetoresistance in single-crystal CoZnO magnetic semiconductors. By quantitative analysis of the transport properties of CoZnO films, it is observed that the positive magnetoresistance in the “hard gap” regime is the result of the carrier wavefunction shrinkage under applied magnetic field. (3) The rectification magnetoresistance in non-magnetic Schottky heterojunctions and the tunneling rectification magnetoresistance in magnetic tunnel junctions. A brand new rectification magnetoresistance is observed in nonmagnetic Al/Ge Schottky heterojunctions: The application of a pure small sinusoidal alternating current to the nonmagnetic Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. Moreover, by using CoO-ZnO composite tunneling barrier, the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated into the Co/CoO-ZnO/Co magnetic tunneling junctions to realize the tunneling rectification magnetoresistance. The observation of rectification magnetoresistance and tunneling rectification magnetoresistance not only adds new members to the magnetoresistance family, but also provides a promising way to control the devices’ properties by using alternating current. In terms of multistate data storage application, this review will introduce: (1) The electrical and magnetic field controllable 4 resistance states in oxide heterojunctions. In Co/CoO-ZnO/Co magnetic tunneling junctions, by integrating the electrical field induced resistance switching and the magnetic field induced tunneling magnetoresistance effects, four nonvolatile resistance states are demonstrated. (2) The remanent magnetization controllable 10 resistance states in magnetic heterojunctions. Here, a general remanent magnetism engineering method is proposed for realizing multiple reliable magnetic and resistance states, not depending on a specific material or device structure. Especially, as a proof-of-concept demonstration, ten states of nonvolatile memory based on the manipulation of ferromagnetic remanent magnetization have been revealed in both Co/Pt magnetic multilayers with strong perpendicular magnetic anisotropy and MgO-based magnetic tunneling junctions at room temperature. (3) The spin-orbit torque controllable 10 resistance states in single-layer magnetic alloy. A repeatable bulk spin-orbit torque switching of the perpendicularly magnetized CoPt alloy single-layer films is realized by introducing a composition gradient in the thickness direction to break the inversion symmetry. Moreover, a ten states nonvolatile memory is illustrated solely by changing the electrical current to control the multi-domain states of the CoPt alloy.

We report an unconventional carrier-dependent anomalous Hall effect (AHE) with a quadratic scaling relation in epitaxial films of a ferromagnetic semiconductor (ZnCo)O with a high Co concentration. We show the co-existence of AHE together with the nonlinear ordinary Hall effect (NLHE) and the separation of NLHE by using a two-conducting channels model in the expression of Hall resistivity. We found that the NLHE depends strongly on both temperature and carrier density n and dominates at low temperature when n

Self-powered UV detectors have attracted intensive research interest due to their advantages of low cost fabrication, high efficiency and low power consumption. In this paper, high ordered SnO2-TiO2 nanoheterostructure arrays were synthesized using soft chemical methods. A self-powered quasi-solid-state UV detector was constructed using this nanoheterostructure as the photoanode and a polyethylene oxide based quasi-solid-state electrolyte as the hole transfer layer. Because the SnO2-TiO2 core-shell nanoheterojunction simultaneously offers a high electron-hole separation, a low charge recombination and a direct pathway for electron transport, the nanostructured self-powered detector displayed an excellent performance over that based on bare TiO2 nanostructure arrays. A quite high incident photon-to-current conversion efficiency of 55.8% at 340 nm and a fast response time (0.14 s for rise time and 0.06 s for decay time) were observed. That is quite excellent performance for self-powered UV detector. Moreover, the self-powered UV photodetector also shows an excellent spectral selectivity and long-time stability in the air. These excellent photoelectric characteristics will enable significant advancements for next-generation photodetecting applications.

Density functional theory within the generalized gradient approximation is employed to investigate the two-dimensional electron gas (2DEG) at the interface of NdGaO3/SrTiO3 (0 0 1) heterostructure. For the superlattice model, the 2DEG originates from the Ti dxy electrons, which are transferred from the NdGaO3 side. However, the interface of the thin film model exhibits insulated properties. In order to investigate the different properties of the two models, it is noted that large polar distortion in the NdGaO3 side occurs in the thin film model comparing to the superlattice model, and the built-in electric field is screened by the large distortion, and result in preventing the electron transfer from the NdGaO3 side to Ti dxy orbitals. For the thin film model, the surface layer of NdGaO3 is the energy favor position of oxygen vacancy, which results in the rotation of the oxygen octahedrons. The 2DEG is induced by the balance between the distortion by the surface and the oxygen octahedrons rotation by the oxygen vacancy.

On the face of the impending energy crisis, developing low-energy consuming photoelectronic devices is extremely important. A wide spectral photosensitivity feature of a self-powered device provides an additional powerful tool. In this letter, a Ag2S/ZnO core-shell nanoheterojunction was prepared and a high performance self-powered solid-state photodetector was developed based on this nanostructure. High quality, vertically aligned ZnO nanoneedle arrays loaded with Ag2S quantum dotes were grown on FTO glass substrate by wet chemical methods. The microstructure and surface morphology of the prepared samples were characterized by transmission electron microscopy and scanning electron microscopy. A solid-state self-powered photodetector was assembled using this ZnO/Ag2S core-shell nanostructure as the photoanode. The photodetector shows a high photosensitivity in the wide spectral range from 400 to 1100 nm, and its response time is as short as 5 ms. Considering its excellent performance and easy fabrication process, this Ag2S/ZnO core-shell nanoheterojunction is an ideal candidate for wide spectral photodetecting application.

Lithium-ion (Li-ion) batteries based on spinel transition-metal oxide electrodes have exhibited excellent electrochemical performance. The reversible intercalation/deintercalation of Li-ions in spinel materials enables not only energy storage but also nondestructive control of the electrodes’ physical properties. This feature will benefit the fabrication of novel Li-ion controlled electronic devices. In this work, reversible control of ferromagnetism was realized by the guided motion of Li-ions in MnFe2O4 and γ-Fe2O3 utilizing miniature lithium-battery devices. The in-situ characterization of magnetization during the Li-ion intercalation/deintercalation process was conducted, and a reversible variation of saturation magnetization over 10% was observed in both these materials. The experimental conditions and material parameters for the control of the ferromagnetism are investigated, and the mechanism related to the magnetic ions’ migration and the exchange coupling evolution during this process was proposed. The different valence states of tetrahedral metal ions were suggested to be responsible for the different performance of these two spinel materials.

While semiconductor spintronics promises lower switching energy and faster speed, a major limitation on its development as a viable technology is the lack of room temperature ferromagnetic semiconductor materials. The material challenge is great, because not only magnetic and electronic doping but also thermally robust coupling between them are required for a room temperature ferromagnetic semiconductor. Here, we report the growth-controlled engineering of magnetic exchange interactions in single crystalline GaCoZnO1-v epitaxial films with high Co concentrations (0.3 ≤ x ≤ 0.45) by controlling oxygen vacancy and carrier density through Ga3+ doping. Strong ferromagnetism, spin-split impurity states, and spin-polarized electrical transport are realized and well controlled at room temperature by tailoring the s,p–d exchange coupling. This room temperature ferromagnetic semiconductor, which offers the ability to individually control carrier density and magnetic doping, will lay a solid foundation for the deve...

In this paper, we demonstrate the ferroelectric gate control of Rashba–Dresselhaus spin–orbit coupling (R–D SOC) in a hybrid heterostructure consisting of a ferromagnetic semiconductor channel (Zn, Co)O(0001) and a ferroelectric substrate PMN-PT(111). The R–D SOC causes a transverse spin current via the charge-spin conversion, which results in unbalanced transverse spin and charge accumulations due to the spin-polarized band in the ferromagnetic (Zn, Co)O channel. By the reversal of gated ferroelectric polarization, we observed 55% modulation of the R–D SOC correlated Hall resistivity to the magnetization correlated anomalous Hall resistivity and 70% modulation of the low-field magnetoresistance at 50 K. Our experimental results pave a way toward semiconductor-based spintronic-integrated circuits with an ultralow power consumption in ferromagnetic semiconductors.

High quality epitaxial rutile Ti 0.95-x Fe 0.05 Nb x O 2−δ (x = 0, 0.01, 0.02, 0.03) films have been grown on (110) MgF 2 substrates by pulsed laser deposition (PLD) method. Detailed experimental characterizations indicate that Nb co-doping in Fe doped TiO 2 gives rise to a shrink of the lattice parameter, an increase of electrical resistivity and a variation of magnetic exchange coupling. These results can be explained by the donor and acceptor co-doping effect. It is supposed that Nb, Fe co-doping in rutile will result in defect-dipole clusters which localizes the free electrons, give rise to an increase of resistivity, and transfer the ferromagnetic exchange to antiferromagnetic exchange. These complex interaction between charge carriers and oxygen vacancies may enrich our understanding of doping mechanism in oxide materials and indicate a new way to explore other novel oxide materials.

Direct evidence of purely interfacial effects on resistance switching is demonstrated in Au/BiFeO3/Nd:SrTiO3(001) (Au/BFO/NSTO) Schottky junctions by reducing the thickness of ferroelectric interlayer BFO. The Au/BFO/NSTO junction shows large current rectification and hysteretic resistive switching behavior without any electroforming process. The conduction mechanism is dominated by interface-limited Fowler–Nordheim (FN) tunneling through a potential barrier formed at the BFO/NSTO interface. Measurements of polarization switching dynamics and capacitance–voltage characteristics provide direct evidence that the resistance switching in the Au/BFO/NSTO junction is ferroelectric and interfacially limited. The observed resistance switching behavior can be attributed to the ferroelectric polarization modulation of the barrier and depletion width of the p–n junction formed at the BFO/NSTO interface.

M-type hexagonal barium ferrite is one of the most favorable ferrite materials, whose functional properties such as ferroelectric polarity alignment and the interaction between electron spins could be controlled by manipulating its stoichiometry or microstructure. In this letter, BaFe 12 O 19 films have been prepared on Al 2 O 3 substrate by pulsed laser deposition at different temperature. AFM and SEM results show that under optimal preparation condition, the films change into self-assembled triangular shaped nano-islands with highly regulated orientation. Interesting magnetic and optical properties have been observed in these BaFe 12 O 19 nanostructures. We believe this work may provide a unique opportunity to investigate anomalous phenomenons associated with nanostructured magnetic oxides and the growth dynamics of ferrite films.

High-quality epitaxial rutile TiO 2 (110) thin films have been fabricated on MgF 2 (110) substrates by pulsed laser deposition (PLD). The samples were characterized with respect to their structural, morphological, and optical properties using various methods such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and UV–Vis spectroscopy. The results demonstrated that the synthesized TiO 2 thin films were pure rutile phase, untwined (110)-oriented epitaxial thin films. In order to test the UV photoresponse of the epitaxial TiO 2 thin film, interdigitated Ni/TiO 2 /Ni structure was designed and fabricated, which exhibits excellent UV response performance. For the spectral response, a maximum of 4.85 A/W occurs at about 300 nm at 5 V applied bias. The UV detector exhibits excellent photoresponse characteristics with a small bias for detecting application in a wide wavelength range.

Atomic-layer two-dimensional (2D) semiconductors are considered as fundamental materials for next-generation nano-optoelectronic devices. Based on the third-order optical nonlinearity, saturable absorption, and band-gap structures of 2D semiconductors, 2D broadband optical switchers were proposed and experimentally constructed for modulating the laser operation, especially in the infrared range; meanwhile, few 2D saturable absorbers in visible lasers were reported. Here, we demonstrate the pulsed green praseodymium (Pr3+) bulk laser at the wavelength of 522 nm modulated by an atomic-layer molybdenum sulfide (MoS2) saturable absorber. The results represent the shortest spectral range in which 2D saturable absorbers applied. Associating with the recent development of visible lasers and previous reported MoS2 saturable absorbers, this letter provides a promising optical modulator for visible lasers and experimentally identifies that the MoS2 saturable absorber is a universal device for laser modulation in the spectral range from the green to mid-infrared.

The first-principles calculations are employed to investigate the electrical properties of (0 0 1) epitaxial LaGaO3/SrTiO3 heterostructure. It is found that the interface remains metallic and the atomic displacements occur mostly in the SrTiO3 side after atomic relaxation. The interface crystal field induces the Ti t2g orbitals to split into the nondegenerate dxy and two-fold degenerate dxz/yz orbitals. The partly filled nondegenerate dxy orbitals are the origin of two-dimensional electron gas at the interface of LaGaO3/SrTiO3 (0 0 1).

Ca{sub 0.98}Dy{sub 0.02}MnO{sub 3} and Ca{sub 0.96}Dy{sub 0.02}Re{sub 0.02}MnO{sub 3} (Re=La, Pr, Sm, Eu, Ho, and Yb) have been synthesized by the solid state reaction method. Samples with relative densities all over 96% have been obtained. Thermoelectric properties are evaluated between 300 and 1000 K. The electrical resistivity shows a typical metal-like conductivity behavior, and at high temperature, 973 K, decreases from 36.1 mΩ cm for Ca{sub 0.98}Dy{sub 0.02}MnO{sub 3} to 8.6 mΩ cm for Ca{sub 0.96}Dy{sub 0.02}Yb{sub 0.02}MnO{sub 3}. Both the absolute values of Seebeck coefficient and thermal conductivity are reduced by the introduction of second rare-earth element. The highest power factor of 415 μW/(K{sup 2}m) is obtained for Ca{sub 0.96}Dy{sub 0.02}Yb{sub 0.02}MnO{sub 3} sample, resulting in the highest dimensionless figure of merit (ZT) 0.25 at 973 K. This value shows an improvement of 144% compared with that of Ca{sub 0.98}Dy{sub 0.02}MnO{sub 3} ceramics at the same temperature. - Graphical abstract: The Ca{sub 0.96}Dy{sub 0.02}Re{sub 0.02}MnO{sub 3} (Re=La, Pr, …, Yb) were prepared by solid state reaction. Highest ZT value obtained is 0.25 at 973 K for Re=Yb, which shows 144% improvement compared with Ca{sub 0.98}Dy{sub 0.02}MnO{sub 3}. - Highlights: • Ca{sub 0.96}Dy{sub 0.02}Re{sub 0.02}MnO{sub 3} (Re=La, Pr, …,more » Yb) are produced by solid state reaction. • Lowest resistivity is obtained due to the highest carrier mobility for Re=Yb. • Highest power factor obtained is 415 μW/(K{sup 2}m) at 973 K for Re=Yb. • Highest ZT value obtained is 0.25 at 973 K for Ca{sub 0.96}Dy{sub 0.02}Yb{sub 0.02}MnO{sub 3} sample.« less

The magnetic and magneto-transport properties of amorphous CoO 1− v films have been systematically studied and manipulated by changing the concentration of oxygen vacancies. A giant exchange bias field H E ≈4380 Oe and a large coercivity H C ≈8500 Oe are observed at 5 K for the composite films. And, a metal to insulator transition has been demonstrated in CoO 1− v films by decreasing the concentration of oxygen vacancies. Moreover, a remarkable decrease of the exchange bias and a slight increase of the saturation magnetization can be obtained by modifying the microstructures through post-thermal annealing.

The density functional theory (DFT) calculations are employed to investigate the effect of in-plane strain on the lattice relaxation and electronic properties of LaAlO3/SrTiO3 interface. It is obtained that the in-plane strain influences the lattice relaxation obviously. The distortion of interfacial Ti–O octahedron is enhanced with the increasing of the in-plane compressive strain. The Ti 3dxy orbital at the interface is partly filled and it is the origin of the interfacial two-dimensional electron gas (2DEG). The in-plane strain can effectively modulate the carrier concentration and consequently the conductivity of the 2DEG formed at the interface. In-plane strain may reduce the carrier concentration significantly and induce a metal-insulator transition when the in-plane compressive (tensile) strain is added up to 4.98% (5.29%).

Manipulation of oxygen vacancies (VO) in transition metal oxides (TMOs) can largely alter their physical and chemical properties, such as electrical conductivity, magnetic state, optical band-gap, and electrocatalytic reactivity. Many experimental and theoretical works have been conducted to study the formation/annihilation of VO and its corresponding effect on the properties in TMOs. In this paper, a solid-state approach to modulate the oxygen stoichiometry in high quality SrCoOx epitaxial thin films was demonstrated. Dependence of the magnetic and electrical conducting properties on VO was investigated. Room temperature reversible phase switching between brownmillerite antiferromagnetic insulating SrCoO2.5 and perovskite ferromagnetic metallic SrCoO3−δ was achieved by electric-field induced oxygen non-stoichiometry. This room temperature reversible phase switching indicates that SrCoOx thin films are a promising candidate for practical applications in resistive random access memory and spintronic devices.

Perovskite-type Ca0.98Dy0.02MnO3, Ca0.96Dy0.04MnO3, and Ca0.96Dy0.02 Re0.02MnO3 (Re = La, Nd, Sm) were prepared by solid-state reaction, and their thermoelectric properties were evaluated between 300 and 1000 K. All were single-phase, with an orthorhombic structure, and had metal-like temperature dependence of resistivity and Seebeck coefficient. The second doping element, Re = La, Nd, or Sm, introduced a larger carrier concentration, leading to a decrease in both resistivity and Seebeck coefficient. This contributed to lower thermal conductivity by introducing a second element into the system. The highest figure of merit, 0.20, was obtained for Re = La at 973 K; this was an increase of almost 100% compared with Ca0.98Dy0.02MnO3 at the same temperature.

Raman scattering spectroscopy has been performed on high quality Co-doped ZnO epitaxial films, which were grown on Al 2 O 3 (0001) by oxygen-plasma assisted molecular beam epitaxy. Raman measurements revealed two local vibration modes (LVMs) at 723 and 699 cm −1 due to the substitution of Co 2+ in wurtzite ZnO lattice. The LVM at 723 cm −1 is found to be an elemental sensitive vibration mode for Co substitution. The LVM at 699 cm −1 can be attributed to enrichment of Co 2+ bound with oxygen vacancy, the cobalt–oxygen vacancy–cobalt complexes, in Zn 1− x Co x O films associated with ferromagnetism. The intensity of LVM at 699 cm −1 , as well as saturated magnetization, enhanced after the vacuum annealing and depressed after oxygen annealing.

The bandgaps of monolayer and bulk molybdenum sulfide (MoS2 ) result in that they are far from suitable for application as a saturable absorption device. In this paper, the operation of a broadband MoS2 saturable absorber is demonstrated by the introduction of suitable defects. It is believed that the results provide some inspiration in the investigation of two-dimensional optoelectronic materials.

The magnetization-direction-dependent inverse spin Hall effect (ISHE) has been observed in NiFe film during spin Seebeck measurement in IrMn/NiFe/Cu/yttrium iron garnet (YIG) multilayer structure, where the YIG and NiFe layers act as the spin injector and spin current detector, respectively. By using the NiFe/IrMn exchange bias structure, the magnetization direction of YIG (M YIG) can be rotated with respect to that of NiFe (M NiFe) with a small magnetic field, thus allowing us to observe the magnetization-direction-dependent inverse spin Hall effect voltage in NiFe layer. Compared with the situation that polarization direction of spin current (σ s) is perpendicular to M NiFe, the spin Seebeck voltage is about 30% larger than that when σ s and M NiFe are parallel to each other. This phenomenon may originate from either or both of stronger interface or bulk scattering to spin current when σ s and M NiFe are perpendicular to each other. Our work provides a way to control the voltage induced by ISHE in ferromagnets.

Cubic Mg 0.45 Zn 0.55 O thin films with MgO buffer layer were epitaxially grown on SrTiO 3 substrate by radio frequency oxygen plasma assisted molecular beam epitaxy. X-ray diffraction measurements indicate high quality single crystal films of (200) orientation. The growth follows cubic-on-cubic alignment with epitaxial relationship of Mg 0.45 Zn 0.55 O (001)[100]//MgO (001)[100]//SrTiO 3 (001)[100]. Atomic force microscopy measurements reveal a smooth surface with the rms roughness of 0.36 nm in an area of 5×5 μm 2 . The band gap of the film is calculated to be 4.8 eV and in the solar blind range. Since the MgO buffer layer can suppress the sub-band-gap photoresponse from the SrTiO 3 substrate and does not absorb moisture like the bare MgO substrate, the Mg 0.45 Zn 0.55 O thin films with MgO buffer layer grown on SrTiO 3 substrate have promising applications in solar blind ultraviolet photodetectors.

ZnO nanoneedle arrays were prepared using a chemical solution route on fluorine-doped SnO 2 conductive glass at low temperature. Crystal structure and morphology of the samples were characterized by X-ray diffraction, scanning electron microscope and high-resolution transmission electron microscope. All the results indicate that high quality ZnO nanoneedles array were grown vertically on the substrates along the (0001) direction. The morphology of the ZnO nanoneedles was controlled by 1-3-diaminopropane concentration. As the concentration of 1-3-diaminopropane increases, transformation from ZnO nanorod to ZnO nanoneedle was realized. Correspondingly, an enhanced field emission property was observed in the ZnO nanoneedle array with sharpertip.

We have fabricated lead free Lix(K0.5Na0.5)(1−x)NbO3 (LKNN) thin films by polyvinylpyrrolidone modified chemical solution deposition, and studied the effects of oxygen ambient on dielectric and ferroelectric properties. The obtained LKNN thin films exhibit significantly improved dielectric properties and saturated ferroelectric hysteresis loop. For LKNN (x = 0.06) thin film, it showed dielectric constant of 471 and dielectric loss of tan δ

Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoS

Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoS2, it can be proposed that MoS2 has the potential as a visible optical modulator. Here, by originally revealing layer-dependent nonlinear absorption of the atomic-layer MoS2 in the visible range, broadband atomic-layer MoS2 optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulators. By applying the selected MoS2 optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this Letter should promote the development of visible ultrafast photonics and further applications of 2D optoelectronic materials.

Photodetectors with excellent detecting properties over a broad spectral range have advantages for the application in many optoelectronic devices. Introducing imperfections to the atomic lattices in semiconductors is a significant way for tuning the bandgap and achieving broadband response, but the imperfection may renovate their intrinsic properties far from the desire. Here, by controlling the deviation from the perfection of the atomic lattice, ultrabroadband multilayer MoS

Strong pinning depends on the pinning force strength and number density of effective defects. Using the hydrostatic pressure method, we demonstrate here that hydrostatic pressure of 1.2 GPa can significantly enhance flux pinning or the critical current density (Jc) of optimally doped Ba0.6K0.4Fe2As2 crystals by a factor of up to 5 in both low and high fields, which is generally rare with other Jc enhancement techniques. At 4.1 K, high pressure can significantly enhance Jc from 5 × 105A/cm2 to nearly 106A/cm2 at 2 T, and from 2 × 105A/cm2 to nearly 5.5 × 105A/cm2 at 12 T. Our systematic analysis of the flux pinning mechanism indicates that both the pinning centre number density and the pinning force are greatly increased by the pressure and enhance the pinning. This study also shows that superconducting performance in terms of flux pinning or Jc for optimally doped superconducting materials can be further improved by using pressure.

In this letter we presented the investigations of magnetodielectric (MD) effect in lead-free multiferroic CoFe 2 O 4 /Na 0.5 K 0.5 NbO 3 (CFO/KNN) bilayers with constant volumes. The CFO/KNN bilayers were synthesized on conductive Nb-doped SrTiO 3 (001) single-crystal substrates by radio frequency magnetron sputtering. Noticeable MD effect was observed in these CFO/KNN bilayers. The MD coefficient depends on the volume fraction of CFO layer. A maximum MD coefficient of about 7% at 12 kOe at 2 kHz was observed in 0.6CFO/0.4 KNN bilayer. The MD effect is attributed to strain-mediated magnetoelectric effect and magnetoresistance effect combined with the Maxwell–Wagner effect. The MD effect may have possible applications in magnetic field sensing devices.

High quality Mn doped ZnO thin films were grown on c-plane Al2O3 by oxygen plasma assisted molecular beam epitaxy. Photoluminescence spectra were investigated on the ferromagnetic ZnMnO films. An additional emission located at ∼3.32 eV was observed on these ferromagnetic films for both as-grown and oxygen-annealed samples. It is assigned to the recombination of neutral acceptor bound excitons. The ionization energy of the acceptor was estimated to be 53–80 meV. The observed ferromagnetism was explained to relate with acceptor-type defects.

A series of FeCoB–SiO2/SiO2 multilayered granular films with various thickness were prepared by alternating co-sputtering FeCoB and SiO2 targets and single-sputtering SiO2 target. As-deposited films were annealed in a magnetic field at different temperature. The high-frequency magnetic and electrical transport properties were investigated. The films annealed above 250 °C show good soft magnetic properties and obvious uniaxial magnetic anisotropy. The resistivity (ρ), coercivity (Hce) decrease and complex permeability ( μ ˜ ), ferromagnetic resonance frequency (fr) increase with increasing annealing temperature and thickness. The desirable high ρ (∼5.92 mΩ cm), considerable frequency linewidth (Δf∼4.02 GHz) and high μ ˜ (μ′=120 at low frequency, μ max ″ = 80 ) were obtained for the 252 nm films annealed at 250 °C. The amorphous or nanograin phase and strong exchange coupling effect are responsible for the good high-frequency magnetic performance. The electrical transport properties show the films with high ρ and large μ ˜ are near the conductive percolation threshold. Moreover, the Δf, damp coefficient (α) and Gilbert damping parameter (G) were discussed based on phenomenological Landau–Lifshitz–Gilbert equation.

We propose a defect-complex model to clarify the origin of ferromagnetism in Co-doped ZnO magnetic semiconductors, based on first-principles calculations. The spin-polarized defect states of oxygen vacancy (V O ) induced by the charge-transfer process are essential to the ferromagnetism. Depending on the charge state of V O and carrier concentration, (V O 2+ + zinc interstitial) and (V O 0 + zinc vacancy) defect complexes are predicted to control the ferromagnetic exchange interaction between the Co ions for insulating and conductive samples, respectively.

We performed first-principles calculations to investigate the electronic structures and magnetic properties of neutral and charged intrinsic defects of wurtzite ZnO. Our results show that an isolated single charged Zn vacancy can introduce a magnetic moment of 1.00 μ B , and may be responsible for the unexpected ferromagnetism in the system.

We report electric field control of the interfacial Dzyaloshinskii-Moriya interaction (DMI) in MgO/Fe/Pt multilayers. The interfacial DMI is obtained and quantified by Brillouin light scattering measurements based on the frequency nonreciprocity of spin waves in a ferromagnet. The magnitude of the induced DMI is found to linearly increase as a function of electric field intensity. The efficiency of electric field control of the interfacial DMI characterized as a ratio of the DMI energy change to the electric field, which is found to be equal to 67 fJ/(Vm) with a positive electric field. We further demonstrate that the origin of the enhanced DMI results from the MgO/Fe interface. The Rashba spin-orbit coupling and electric field induced anisotropy at the MgO/Fe interface might be responsible for the enhanced interfacial DMI. Our findings open up a way for exploring the spintronic devices with a tunable DMI.