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Heterostructures composed of dissimilar oxides with different properties offer opportunities to develop emergent devices with desired functionalities. A key feature of oxide heterostructures is interface electronics and orbital reconstructions. Here, we combined infinite-layered SrCuO2 and perovskite SrRuO3 into heterostructures. A rare high spin state as large as 3.0 μB f.u-1 and an increase in Curie temperature by 12 K are achieved in an ultrathin SrRuO3 film capped by a SrCuO2 layer. Atomic-scale lattice imaging shows the uniform CuO2-plane-to-RuO5-pyramid connection at the interface, where the regularly arranged RuO5 pyramids were elongated along the out-of-plane direction. As revealed by theoretical calculations and spectral analysis, these features finally result in an abnormally high spin state of the interfacial Ru ions with highly polarized eg orbitals. The present work demonstrates that oxygen coordination engineering at the infinite-layer/perovskite oxide interface is a promising approach towards advanced oxide electronics.

The recent discovery of van der Waals magnetic materials has attracted great attention in materials science and spintronics. The preparation of ultrathin magnetic layers down to atomic thickness is challenging and is mostly by mechanical exfoliation. Here, we report vapor deposition of magnetic van der Waals NiI2 crystals. Two-dimensional (2D) NiI2 flakes are grown on SiO2/Si substrates with a thickness of 5-40 nm and on hexagonal boron nitride (h-BN) down to monolayer thickness. Temperature-dependent Raman spectroscopy reveals robust magnetic phase transitions in the as-grown 2D NiI2 crystals down to trilayer. Electrical measurements show a semiconducting transport behavior with a high on/off ratio of 106 for the NiI2 flakes. Lastly, density functional theory calculation shows an intralayer ferromagnetic and interlayer antiferromagnetic ordering in 2D NiI2. This work provides a feasible approach to epitaxy 2D magnetic transition metal halides and also offers atomically thin materials for spintronic devices.

To incorporate spintronics functionalities into two-dimensional devices, it is strongly desired to get two-dimensional electron gases (2DEGs) with high spin polarization. Unfortunately, the magnetic characteristics of the typical 2DEG at the LaAlO

Bilinear magnetoresistance (BMR), the magnetoresistance that is linear against either magnetic field or applied current, is a hot topic of recent investigations. While most of the previous works focused on isotropic BMR, here we report on a strongly anisotropic BMR for (110) $\mathrm{SrTi}{\mathrm{O}}_{3}$-based two-dimensional electron gas (2DEG). Remarkably, the BMR measured along the [001] axis can be fivefold as large as that obtained along the $[1\overline{1}0]$ axis. A close relation is found between BMR and current-induced effective Rashba field, and it is the anisotropy of the Rashba field that causes the anisotropic BMR. Based on the analysis of anisotropic magnetoresistance, effective Rashba fields up to 4.5 T are determined. The band structure of the 2DEG is further calculated, ellipse-shaped Fermi rings are obtained, and the respective effects of different Fermi rings on BMR are distinguished. This work demonstrates the great potential of anisotropic 2DEG for the exploration of unusual effects.

Interface engineering is an effective and feasible method to regulate the magnetic anisotropy of films by altering interfacial states between different films. Using the technique of pulsed laser deposition, we prepared La0.67Sr0.33MnO3 (LSMO) and La0.67Sr0.33MnO3/SrCoO2.5 (LSMO/SCO) films on the (110)-oriented La0.3Sr0.7Al0.65Ta0.35O3 substrates. By covering the SCO film above the LSMO film, we transformed the easy magnetization axis of LSMO from the [001] axis to the [1\(\stackrel{\text{-}}{\text{1}}\)0] axis in the film plane. Based on statistical analyses, we found that the corresponding Mn-Mn ionic distances are different in the two types of LSMO films, causing different distortions of Mn-O octahedron in the LSMO film. In addition, it also induces diverse electronic occupation states in Mn3+ ions. The eg electron of Mn3+ occupies 3z2-r2 and x2-y2 orbitals in the LSMO and LSMO/SCO, respectively. We conclude that the electronic spin reorientation leads to the transformation of the easy magnetization axis in the LSMO films.

With the help of the two-dimensional electron gas (2DEG) at the LaAlO3–SrTiO3 interface, spin and charge currents can be interconverted. However, the conversion efficiency has been strongly depressed by LaAlO3, which blocks spin transmission. It is therefore highly desired to explore 2DEGs sandwiched between ferromagnetic insulators that are transparent for magnons. By constructing epitaxial heterostructure with ferromagnetic EuO, which is conducting for spin current but insulating for electric current, and KTaO3, we successfully obtained the 2DEGs, which can receive thermally injected spin current directly from EuO and convert the spin current to charge current via inverse Edelstein effect of the interface. Strong dependence of the spin Seebeck coefficient on the layer thickness of EuO is further observed and the propagation length for non-equilibrium magnons in EuO has been determined. The present work demonstrates the great potential of the 2DEGs formed by ferromagnetic oxides for spin caloritronics.

Controlling electronic processes in low-dimension electron systems is centrally important for both fundamental and applied researches. While most of the previous works focused on SrTiO3-based two-dimensional electron gases (2DEGs), here we report on a comprehensive investigation in this regard for amorphous-LaAlO3/KTaO3 2DEGs with the Fermi energy ranging from ∼13 meV to ∼488 meV. The most important observation is the dramatic variation of the Rashba spin–orbit coupling (SOC) as Fermi energy sweeps through 313 meV: The SOC effective field first jumps and then drops, leading to a cusp of ∼2.6 T. Above 313 meV, an additional species of mobile electrons emerges, with a 50-fold enhanced Hall mobility. A relationship between spin relaxation distance and the degree of band filling has been established in a wide range. It indicates that the maximal spin precession length is ∼70.1 nm and the maximal Rashba spin splitting energy is ∼30 meV. Both values are much larger than the previously reported ones. As evidence...

Interface engineering is an effective and feasible method to regulate the magnetic anisotropy of films by altering interfacial states between films. Using the technique of pulsed laser deposition, we prepared La0.67Sr0.33MnO3 (LSMO) and La0.67Sr0.33MnO3/SrCoO2.5 (LSMO/SCO) films on (110)-oriented La0.3Sr0.7Al0.65Ta0.35O3 substrates. By covering the SCO film above the LSMO film, we transformed the easy magnetization axis of LSMO from the [001] axis to the [ 1 1 ¯ 0 ] axis in the film plane. Based on statistical analyses, we find that the corresponding Mn–Mn ionic distances are different in the two types of LSMO films, causing different distortions of Mn–O octahedron in LSMO. In addition, it also induces diverse electronic occupation states in Mn3+ ions. The e g electron of Mn3+ occupies 3z 2 – r 2 and x 2 – y 2 orbitals in the LSMO and LSMO/SCO, respectively. We conclude that the electronic spin reorientation leads to the transformation of the easy magnetization axis in the LSMO films.

Two-dimensional electron gas (2DEG) at the perovskite oxide interface exhibits a lot of exotic properties, presenting a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO3-based 2DEG, here we report on the fabrication of high-quality 2DEGs by growing an amorphous LaAlO3 layer on a (001)-orientated KTaO3 substrate, which is a 5d metal oxide with a polar surface, at a high temperature that is usually adopted for crystalline LaAlO3. Metallic 2DEGs with a Hall mobility as high as ∼2150 cm2/(V s) and a sheet carrier density as low as 2 × 1012 cm–2 are obtained. For the first time, the gating effect on the transport process is studied, and its influence on spin relaxation and inelastic and elastic scattering is determined. Remarkably, the spin relaxation time can be strongly tuned by a back gate. It is reduced by a factor of ∼69 while the gate voltage is swept from −25 to +100 V. The mechanism that dominates the spin relaxation is elucidated.

Being able to tune magnetic anisotropy (MA) by an electric field is crucial for the development of low-power magnetoelectric devices. The authors present an approach for tuning the MA of a manganite film by modulating the crystal phase of a cobaltite cap layer. By driving the cap layer to switch between SrCoO${}_{2.5}$ and SrCoO${}_{3\ensuremath{-}\ensuremath{\delta}}$ structures, reversible tuning of MA between two crystal directions was achieved for the manganite layer, accompanying a change in Mn $3d$ orbital occupancy. This work demonstrates indirect tuning of the magnetic easy axis of this highly spin-polarized manganite, providing guidance for constructing electrically tunable magnetoelectric devices.

Perpendicular magnetic anisotropy (PMA) of magnetic materials has received much attention because of its potential application to spintronics devices. In general, the tensely strained $(001)\text{\ensuremath{-}}\mathrm{L}{\mathrm{a}}_{2/3}\mathrm{S}{\mathrm{r}}_{1/3}\mathrm{Mn}{\mathrm{O}}_{3}$ (LSMO) layer is easy plane. Here we demonstrate that the tensile LSMO layer will exhibit an out-of-plane magnetic anisotropy if it is sandwiched between two $\mathrm{L}{\mathrm{a}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{r}}_{x}\mathrm{Co}{\mathrm{O}}_{2.5+\ensuremath{\delta}}$ (LSCO) layers. The most remarkable observation is that the PMA enhances with the increase of the Sr content in LSCO. It is $\ensuremath{\sim}2.7\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.16em}{0ex}}\mathrm{erg}/\mathrm{c}{\mathrm{m}}^{3}$ for $x=0.05$ and $\ensuremath{\sim}4.3\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.16em}{0ex}}\mathrm{erg}/\mathrm{c}{\mathrm{m}}^{3}$ for $x=0.5$. This value is two orders of magnitude greater than that obtained by compressively straining the LSMO film $(\ensuremath{\sim}{10}^{4}\phantom{\rule{0.16em}{0ex}}\mathrm{erg}/\mathrm{c}{\mathrm{m}}^{3})$. Analysis of high resolution lattice image shows the formation of perovskite/brownmillerite-type interfaces in the multilayers: Brownmillerite-like lattice structure forms in the interfacial layers of LSCO, resulting in a coherent tilting of adjacent $\mathrm{Mn}{\mathrm{O}}_{6}$ octahedra. This in turn leads to, as evidenced by the analysis of x-ray linear dichroism, selective orbital occupation thus spin reorientation. There is evidence that the brownmillerite-structured LSCO is more easily formed when $x$ is high, which explains the growth of anisotropy constant with the increase of Sr content.

Brownmillerite oxides ($A\mathrm{B}{\mathrm{O}}_{2.5}$) with long-range ordering of oxygen vacancies own a distinct superstructure formed by alternately stacked octahedral $\mathrm{B}{\mathrm{O}}_{6}$ and tetrahedral $\mathrm{B}{\mathrm{O}}_{4}$ planes. The one-dimensional oxygen vacancy channels within $\mathrm{B}{\mathrm{O}}_{4}$ layers usually lead to high ionic conductivity of brownmillerite oxides, demonstrating great application potential in solid-oxide fuel cells, the oxygen separation membrane, and catalyzers. Here, high quality brownmillerite-$\mathrm{SrCo}{\mathrm{O}}_{2.5}$ films have been epitaxially grown on differently oriented substrates by pulsed laser deposition. The anisotropic structural and physical properties of (110)- and (111)-oriented $\mathrm{SrCo}{\mathrm{O}}_{2.5}$ films were systematically investigated. We found, unlike the out-of-plane (001)-oriented $\mathrm{SrCo}{\mathrm{O}}_{2.5}$ films, the $\mathrm{Co}{\mathrm{O}}_{6}$ and $\mathrm{Co}{\mathrm{O}}_{4}$ planes would alternately stack along one of the [100] and [010] axes for (110)-oriented films and one of the [100], [010], and [001] axes for (111)-oriented films, forming coexisting crystal domains with different orientations. More importantly, the superstructure of these films could be reversibly tuned by alternately applying an electric field along two orthogonal directions, switching between an ordered and a disordered state. Corresponding to structural anisotropy, strong in-plane electronic anisotropy of the (110)-oriented $\mathrm{SrCo}{\mathrm{O}}_{2.5}$ film was revealed, which was also electrically tunable like the superstructure. This work demonstrates the approaches to modify the ionic conduction channels of brownmillerite oxides, opening avenues towards electrically tunable oxygen separation membrane and catalyzers.

Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators present a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO3-based 2DEGs, here we took the amorphous-ABO3/KTaO3 system as the research object to study the relationship between the interface conductivity and the redox property of B-site metal in the amorphous film. The criterion of oxide–oxide interface redox reactions for the B-site metals, Zr, Al, Ti, Ta, and Nb in conductive interfaces was revealed: the formation heat of metal oxide, Δ H f o , is lower than –350 kJ/(mol O) and the work function of the metal Φ is in the range of 3.75 eV < Φ < 4.4 eV. Furthermore, we found that the smaller absolute value of Δ H f o and the larger value of Φ of the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO3/KTaO3 interface. This finding paves the way for the design of high-mobility all-oxide electronic devices.

Laboratory-based in vitro antimicrobial susceptibility testing is the foundation for guiding anti-infective therapy and monitoring antimicrobial resistance trends. We used whole-genome sequencing (WGS) technology to identify known antimicrobial resistance determinants among strains of nontyphoidal Salmonella and correlated these with susceptibility phenotypes to evaluate the utility of WGS for antimicrobial resistance surveillance. Six hundred forty Salmonella of 43 different serotypes were selected from among retail meat and human clinical isolates that were tested for susceptibility to 14 antimicrobials using broth microdilution. The MIC for each drug was used to categorize isolates as susceptible or resistant based on Clinical and Laboratory Standards Institute clinical breakpoints or National Antimicrobial Resistance Monitoring System (NARMS) consensus interpretive criteria. Each isolate was subjected to whole-genome shotgun sequencing, and resistance genes were identified from assembled sequences. A total of 65 unique resistance genes, plus mutations in two structural resistance loci, were identified. There were more unique resistance genes ( n = 59) in the 104 human isolates than in the 536 retail meat isolates ( n = 36). Overall, resistance genotypes and phenotypes correlated in 99.0% of cases. Correlations approached 100% for most classes of antibiotics but were lower for aminoglycosides and beta-lactams. We report the first finding of extended-spectrum β-lactamases (ESBLs) ( bla CTX-M1 and bla SHV2a ) in retail meat isolates of Salmonella in the United States. Whole-genome sequencing is an effective tool for predicting antibiotic resistance in nontyphoidal Salmonella , although the use of more appropriate surveillance breakpoints and increased knowledge of new resistance alleles will further improve correlations.

Heterostructure with a symmetry-mismatched interface provides a promising playground for the exploration of emergent phenomena. Herein, we report a systematic investigation on La2/3Sr1/3MnO3/YBaCo2O5+δ (LSMO/YBCO) grown on SrTiO3, a heterostructure formed by perovskite oxides of different symmetry. A high-resolution lattice image shows the formation of high-quality perovskite LSMO and A-site cation-ordered oxygen-deficient double perovskite YBCO, without any signatures of atomic reconfiguration at the interface. Surprisingly, the YBCO-buffered LSMO exhibits perpendicular magnetic anisotropy (PMA), though bare LSMO film is in-plane anisotropic. The PMA is robust, appearing even when the thickness of YBCO is only one unit cell. The typical anisotropy constant is ∼4 × 106 erg cm−3. X-ray absorption spectroscopy analysis reveals a preferential occupation of the d 3 z 2 − r 2 orbital compared with d x 2 − y 2 , which is confirmed by density functional theory calculations. This orbital reconstruction accounts for the PMA. The formation of a covalent bond between Mn and Co caged by different oxygen polyhedrons, an octahedron and a square pyramid, respectively, stabilizes the orbital reconstruction, resulting in anomalous spin orientation.

The electric gating on the transport properties of two-dimensional electron gas (2DEG) at the interface of LaAlO3/SrTiO3 (LAO/STO) heterostructure has attracted great research interest due to its potential application in field-effect devices. Most of previous works of gate effect were focused on the LAO/STO heterostructure containing only one conductive interface. Here, we systematically investigated the gate effect on high-quality LAO/STO superlattices (SLs) fabricated on the TiO2-terminated (001) STO substrates. In addition to the good metallicity of all SLs, we found that there are two types of charge carriers, the majority carriers and the minority carriers, coexisting in the SLs. The sheet resistance of the SLs with a fixed thickness of the LAO layer increases monotonically as the thickness of the STO layer increases. This is derived from the dependence of the minority carrier density on the thickness of STO. Unlike the LAO/STO heterostructure in which minority and majority carriers are simultaneously modulated by the gate effect, the minority carriers in the SLs can be tuned more significantly by the electric gating while the density of majority carriers is almost invariable. Thus, we consider that the minority carriers may mainly exist in the first interface near the STO substrate that is more sensitive to the back-gate voltage, and the majority carriers exist in the post-deposited STO layers. The SL structure provides the space separation for the multichannel conduction in the 2DEG, which opens an avenue for the design of field-effect devices based on LAO/STO heterostructure.

Grouping different oxide materials with coupled charge, spin, and orbital degrees of freedom together to form heterostructures provides a rich playground to explore the emergent interfacial phenomena. The perovskite/brownmillerite heterostructure is particularly interesting since symmetry mismatch may produce considerable interface reconstruction and unexpected physical effects. Here, we systemically study the magnetic anisotropy of tensely strained La2/3Sr1/3Co1 – x Mn x O2.5 + δ /La2/3Sr1/3MnO3/La2/3Sr1/3Co1 – x Mn x O2.5 + δ trilayers with interface structures changing from perovskite/brownmillerite type to perovskite/perovskite type. Without Mn doping, the initial La2/3Sr1/3CoO2.5 + δ /La2/3Sr1/3MnO3/La2/3Sr1/3CoO2.5 + δ trilayer with perovskite/brownmillerite interface type exhibits perpendicular magnetic anisotropy and the maximal anisotropy constant is 3.385 × 106 erg/cm3, which is more than one orders of magnitude larger than that of same strained LSMO film. By increasing the Mn doping concentration, the anisotropy constant displays monotonic reduction and even changes from perpendicular magnetic anisotropy to in-plane magnetic anisotropy, which is possible because of the reduced CoO4 tetrahedra concentration in the La2/3Sr1/3Co1 – x Mn x O2.5 + δ layers near the interface. Based on the analysis of the x-ray linear dichroism, the orbital reconstruction of Mn ions occurs at the interface of the trilayers and thus results in the controllable magnetic anisotropy.

With the help of the two-dimensional electron gas (2DEG) at the LaAlO

Interface engineering is an important approach leading to multifunctional artificial materials. Although most of the previous works focused on the effects of the rotation/tilting of interfacial oxygen octahedron on perovskite multilayers, here, we report on a new kind of lattice distortion characterized by an off-center shift of the Mn ions within the MnO

Two-dimensional electron gases (2DEGs) at oxide interfaces, which provide unique playgrounds for emergent phenomena, have attracted increasing attention in recent years. While most of the previous works focused on the 2DEGs at ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ interfaces, here we report on a new kind of 2DEGs formed between a magnetic insulator EuO and a high-$k$ perovskite ${\mathrm{KTaO}}_{3}$. The 2DEGs are not only highly conducting, with a maximal Hall mobility of $111.6\text{ }\text{ }{\mathrm{cm}}^{2}/\mathrm{V}\text{ }\mathrm{s}$ at 2 K, but also well spin polarized, showing strongly hysteretic magnetoresistance up to 25 K and well-defined anomalous Hall effect up to 70 K. Moreover, unambiguous correspondences between the hysteretic behaviors of 2DEGs and the EuO layer are captured, suggesting the proximity effect of the latter on the former. This is confirmed by the results of density-functional theory calculations: Through interlayer exchange, EuO drives the neighboring ${\mathrm{TaO}}_{2}$ layer into a ferromagnetic state. The present work opens new avenues for the exploration for high performance spin-polarized 2DEGs at oxide interfaces.

Two-dimensional electron gases (2DEGs) at oxide interfaces, which provide unique playgrounds for emergent phenomena, have attracted increasing attention in recent years. While most of the previous works focused on the 2DEGs at LaAlO_{3}/SrTiO_{3} interfaces, here we report on a new kind of 2DEGs formed between a magnetic insulator EuO and a high-k perovskite KTaO_{3}. The 2DEGs are not only highly conducting, with a maximal Hall mobility of 111.6 cm^{2}/V s at 2 K, but also well spin polarized, showing strongly hysteretic magnetoresistance up to 25 K and well-defined anomalous Hall effect up to 70 K. Moreover, unambiguous correspondences between the hysteretic behaviors of 2DEGs and the EuO layer are captured, suggesting the proximity effect of the latter on the former. This is confirmed by the results of density-functional theory calculations: Through interlayer exchange, EuO drives the neighboring TaO_{2} layer into a ferromagnetic state. The present work opens new avenues for the exploration for high performance spin-polarized 2DEGs at oxide interfaces.

Spin-polarized two-dimensional electron gas (2DEG) at the interface of two insulating perovskite oxides has been a focus of intensive studies in recent years. So far all attempts to construct magnetic 2DEG are based on the selection of an appropriate buffer layer or cap layer in $\mathrm{SrTi}{\mathrm{O}}_{3}$-based heterostructures, and the magnetic effect thus produced on 2DEG is indirect and weak. Here, we fabricated the 2DEG based on Fe-doped $\mathrm{SrTi}{\mathrm{O}}_{3}$ that is superparamagnetic rather than diamagnetic like $\mathrm{SrTi}{\mathrm{O}}_{3}$. In addition to good metallicity, considerable Kondo effect, and negative magnetoresistance, the most striking observation of the present work is the occurrence of the anomalous Hall effect up to room temperature. This is transport evidence for the existence of spin-polarized 2DEG at high temperatures. As suggested by the monotonic increase of Curie temperature with carrier density, the magnetic exchange between magnetic ions could be mediated by the itinerant electrons of the 2DEG. The present work opens an avenue for the exploration of spin-polarized 2DEG.

Objectives To understand the molecular epidemiology of gentamicin-resistant Campylobacter and investigate aminoglycoside resistance mechanisms. Methods One-hundred-and-fifty-one gentamicin-resistant Campylobacter isolates from humans (n = 38 Campylobacter jejuni; n = 41, Campylobacter coli) and retail chickens (n = 72 C. coli), were screened for the presence of gentamicin resistance genes by PCR and subtyped using PFGE. A subset of the isolates (n = 41) was analysed using WGS. Results Nine variants of gentamicin resistance genes were identified: aph(2″)-Ib, Ic, Ig, If, If1, If3, Ih, aac(6′)-Ie/aph(2″)-Ia and aac(6′)-Ie/aph(2″)-If2. The aph(2″)-Ib, Ic, If1, If3, Ih and aac(6′)-Ie/aph(2″)-If2 variants were identified for the first time in Campylobacter. Human isolates showed more diverse aminoglycoside resistance genes than did retail chicken isolates, in which only aph(2″)-Ic and -Ig were identified. The aph(2″)-Ig gene was only gene shared by C. coli isolates from human (n = 27) and retail chicken (n = 69). These isolates displayed the same resistance profile and similar PFGE patterns, suggesting that contaminated retail chicken was probably the source of human C. coli infections. Human isolates were genetically diverse and generally more resistant than the retail chicken isolates. The most frequent co-resistance was to tetracycline (78/79, 98.7%), followed by ciprofloxacin/nalidixic acid (46/79, 58.2%), erythromycin and azithromycin (36/79, 45.6%), telithromycin (32/79, 40.5%) and clindamycin (18/79, 22.8%). All human and retail meat isolates were susceptible to florfenicol. Conclusions This study demonstrated that several new aminoglycoside resistance genes underlie the recent emergence of gentamicin-resistant Campylobacter, and that, in addition to contaminated retail chicken, other sources have also contributed to gentamicin-resistant Campylobacter infections in humans.

Two-dimensional electron gas (2DEG) at the perovskite oxide interface exhibits a lot of exotic properties, presenting a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO

Highly mobile 2-dimensional electron gases (2DEGs) at the (001), (011) and (111)-oriented LaAlO

The mechanism of resistive switching in metal oxides is a widely studied topic with interest in both fundamental physics and the practical need to improve device characteristics for memory based applications. Various experimental approaches were employed to reveal the different aspects of resistive switching; however, there is still a debate on the switching mechanism due to the lack of nondestructive microscopic characterization tools to monitor the oxygen vacancies. In this study, a novel approach using photoluminescence (PL) mapping was developed to study switching dynamics in metal oxides. By monitoring the emission properties with a confocal PL system, information regarding the switching mechanism can be obtained. The nondestructive nature of this approach allowed us to make comparisons between different switching conditions and endurance cycles. SrTiO3 based switching devices were used in the study. The distribution of oxygen vacancies can be positioned by mapping the integrated intensity of oxygen vacancy emission on a transparent top electrode, and both interface switching and filament switching can be distinguished. Moreover, the endurance study revealed a sudden rise in the emission intensity correlated with the device failure, which indicates an abrupt increase in the localized density of oxygen vacancies that results in an irreversible set process for the conductive filament.

Applying conductive silver paint to the surface of a 0.1 wt% Nb-doped SrTiO3 (STON) substrate resulted in an Ag/STON junction device. By applying electric current pulses to the junction, multiple resistance states ranging from high resistance (R≈75 kΩ) to low resistance (R≈2 kΩ) were observed. By alternating the electric pulses, the Ag/STON junctions oscillated between the two resistance states, which has potential applications in memory devices. Current–voltage (I–V) measurements were performed to study the interface between the Ag and STON substrate. The interface characteristics were dependent on the resistance state and could be easily controlled by the electric pulse. When the high-resistance state transitioned to the low-resistance state, a change from a Schottky-like to Ohmic contact was detected. These electric-pulse-induced variations in the I–V relationship may be interesting for applications such as multi-channel I–V transformers.

A series of Pr 0.5 Sr 0.5 MnO 3 (PSMO) films with various thickness were epitaxially grown on substrates of (0 0 1)-oriented (LaAlO 3 ) 0.3 (SrAl 0.5 Ta 0.5 O 3 ) 0.7 (LSAT), LaAlO 3 (LAO) and SrTiO 3 (STO), and (0 1 1)-oriented STO using pulse laser deposition. Influence of epitaxial growth on phase competition was investigated. A ferromagnetic metal to antiferromagnetic insulator (FMM–AFI) transition upon cooling is present in both largely compressed situations deposited on LAO (0 0 1) and tensile cases deposited on STO (0 0 1) but absent in little strained films grown on LSAT (0 0 1), indicating that the antiferromagnetic insulating state is favored by strains. On the other hand, the 400 nm films deposited on (0 1 1)-oriented STO as well as LAO substrates show FMM–AFI transition. These results reveal that both the orientation of epitaxial growth and substrate-induced strain affect the FMM–AFI transition.

Based on a unified physical model and first-principle calculations, a material-oriented methodology has been proposed to control the bipolar switching behavior of an oxide-based resistive random access memory (RRAM) cell. According to the material-oriented methodology, the oxide-based RRAM cell can be designed by material engineering to achieve the required device performance. In this article, a Gd-doped HfO2 RRAM cell with excellent bipolar switching characteristics is developed to meet the requirements of memristive device application. The typical memristive characteristics of the Gd-doped HfO2 RRAM cell are presented, and the mechanism is discussed.

High mobility spin-polarized two-dimensional electron gas (2DEG) is crucially important for spintronic applications. Here, we report our investigations on the 2DEG fabricated by spin coating a LaAlO3 layer on a (001) SrTiO3 substrate with a La2/3Sr1/3MnO3 buffer layer. When the buffer layer is below 3 uc, the 2DGE is highly mobile. Corresponding to the layer thicknesses of 0, 1, and 2 uc, the Hall mobilities are ∼24 000 cm2/V s, ∼28 000 cm2/V s, and ∼59 600 cm2/V s at 2 K. In contrast, the 2DEG with a buffer layer of 3 uc shows a relatively low mobility (∼3000 cm2/V s). However, an anomalous Hall effect was observed in this 2DEG below 20 K, indicating a long range ferromagnetic order. This work demonstrates the great potential of the chemical method in gaining high quality spin-polarized 2DEGs at the LaAlO3/SrTiO3 interface.