Epitaxial La0.7Sr0.3MnO3(LSMO)/La0.7Sr0.3FeO3 (LSFO) superlattices serve as model systems to explore the magnetic structure and exchange coupling at (111)-oriented perovskite oxide interfaces. The (111) orientation possesses a buckled honeycomb structure resembling that of graphene with the stacking of highly polar layers. Furthermore, the bulk LSFO magnetic structure suggests that an ideal (111) interface should have fully uncompensated antiferromagnetic (AF) moments leading to exchange bias interactions. Detailed soft x-ray magnetic spectroscopy and microscopy reveal that interfacial effects and ultrathin superlattice sublayers can stabilize orientations of the LSFO AF spin axis, which differ from that of LSFO films and LSMO/LSFO bilayers. A portion of the AF moments can be reoriented to an arbitrary direction by a moderate external magnetic field through spin-flop coupling with the ferromagnetic LSMO sublayers that have low magnetocrystalline anisotropy in the (111) plane.

Investment in brighter sources and larger and faster detectors has accelerated the speed of data acquisition at national user facilities. The accelerated data acquisition offers many opportunities for the discovery of new materials, but it also presents a daunting challenge. The rate of data acquisition far exceeds the current speed of data quality assessment, resulting in less than optimal data and data coverage, which in extreme cases forces recollection of data. Herein, we show how this challenge can be addressed through the development of an approach that makes routine data assessment automatic and instantaneous. By extracting and visualizing customized attributes in real time, data quality and coverage, as well as other scientifically relevant information contained in large data sets, is highlighted. Deployment of such an approach not only improves the quality of data but also helps optimize the usage of expensive characterization resources by prioritizing measurements of the highest scientific impact. We anticipate our approach will become a starting point for a sophisticated decision-tree that optimizes data quality and maximizes scientific content in real time through automation. With these efforts to integrate more automation in data collection and analysis, we can truly take advantage of the accelerating speed of data acquisition.

The extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La_0.7Sr_0.3MnO₃/La_0.7Sr_0.3CoO₃ ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5-6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers. The saturation magnetization and coercivity depends sensitively on the sublayer thickness due to the length scale of this interfacial effect. For larger sublayer thicknesses, the La_0.7Sr_0.3MnO₃ and La_0.7Sr_0.3CoO₃ sublayers are magnetically decoupled, displaying two independent magnetic transitions with little sublayer thickness dependence. These results demonstrate how interfacial phenomena at perovskite oxide interfaces can be used to tailor their functional properties at the atomic scale.

We report on the observation of exchange-spring behavior in complex oxide bilayers composed of high coercivity ferromagnetic (FM) La0.7Sr0.3CoO3 (LSCO) and low coercivity FM La0.7Sr0.3MnO3 (LSMO). The magnetization process from each individual layer is revealed by a combination of bulk magnetometry and x-ray magnetic circular dichroism measurements. The results show unexpected magnetic switching behavior which deviates from conventional exchange-spring systems in that reversible switching occurs not only within the soft LSMO layer but is also accompanied by the switching of an interfacial LSCO layer. The origin of such exchange coupling is discussed in terms of charge redistribution at the interface.

Al-substituted Li7La3Zr2O12 samples processed under argon show enhanced Li-ion transport and interfacial properties in symmetrical cells with lithium electrodes, compared to those prepared in air. In particular, the samples prepared under argon have higher ionic conductivities and lower interfacial impedances in symmetrical lithium cells, and show better DC cycling characteristics. The electronic conductivities are also somewhat higher. Pellets subjected to thermal treatment under the two types of atmospheres have different colors but exhibit similar microstructures. X-ray diffraction experiments suggest that there are slight structural differences between the two types of samples, but few dissimilarities were observed in elemental composition, distribution of ions, oxidation states, or bond lengths using laser-induced breakdown spectroscopy (LIBS), x-ray photoelectron spectroscopy (XPS), and extended x-ray absorption fine structure spectroscopy (EXAFS) to analyze the materials. Additionally, there was no evidence that La or Zr were reduced during the processing under Ar. Possible explanations for the improved electrochemical properties of the sample prepared under Ar compared to the one prepared in air include differences in grain boundary chemistries and conductivities and/or a small concentration of oxygen vacancies in the former.

The impact of interfacial electronic reconstruction on the magnetic characteristics of La0.7Sr0.3CoO3 (LSCO)/La0.7Sr0.3MnO3 (LSMO) heterostructures was investigated as a function of layer thickness using a combination of soft x-ray magnetic spectroscopy and bulk magnetometry. We found that the magnetic properties of the LSCO layers are impacted by two competing electronic interactions occurring at the LSCO/substrate and LSMO/LSCO interfaces. For thin LSCO layers (<5 nm), the heterostructures exist in a highly coupled state where the chemically distinct layers behave as a single magnetic compound with magnetically active Co2+ ions. As the LSCO thickness increases, a high coercivity LSCO layer develops which biases a low coercivity layer, which is composed not only of the LSMO layer but also an interfacial LSCO layer. These results suggest an intriguing route to tune the magnetic properties of transition metal oxide heterostructures through careful control of the interface structure.

Ancient Jian wares are famous for their lustrous black glaze that exhibits unique colored patterns. Some striking examples include the brownish colored "Hare's Fur" (HF) strips and the silvery "Oil Spot" (OS) patterns. Herein, we investigated the glaze surface of HF and OS samples using a variety of characterization methods. Contrary to the commonly accepted theory, we identified the presence of ε-Fe2O3, a rare metastable polymorph of Fe2O3 with unique magnetic properties, in both HF and OS samples. We found that surface crystals of OS samples are up to several micrometers in size and exclusively made of ε-Fe2O3. Interestingly, these ε-Fe2O3 crystals on the OS sample surface are organized in a periodic two dimensional fashion. These results shed new lights on the actual mechanisms and kinetics of polymorphous transitions of Fe2O3. Deciphering technologies behind the fabrication of ancient Jian wares can thus potentially help researchers improve the ε-Fe2O3 synthesis.

Epitaxial La0.7Sr0.3MnO3(LSMO)/La0.7Sr0.3FeO3 (LSFO) superlattices on (111)-oriented SrTiO3 substrates with sublayer thicknesses ranging from 3 to 60 unit cells (u.c.) were synthesized and characterized. Detailed analysis of their structural, electronic, and magnetic properties were performed to explore the effect of sublayer thickness on the magnetic structure and exchange coupling at (111)-oriented perovskite oxide interfaces. In the ultrathin limit (3-6 u.c.), we find that the antiferromagnetic (AF) properties of the LSFO sublayers are preserved with an out-of-plane canting of the AF spin axis, while the ferromagnetic (FM) properties of the LSMO sublayers are significantly depressed. For thicker LSFO layers (>9 u.c.), the out-of-plane canting of the AF spin axis is only present in superlattices with thick LSMO sublayers. As a result, exchange coupling in the form of spin-flop coupling exists only in superlattices which display both robust ferromagnetism and out-of-plane canting of the AF spin axis.

Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO3, through the careful control of the biaxial strain state and TiO6 octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO3 films grown on La0.18Sr0.82Al0.59Ta0.41O3 (LSAT) and NdGaO3 (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO6 octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4?mm phase with remnant polarization ∼5?μC/cm2 at 10?K and Tc near 140?K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and Tc. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.