Strain-Induced Domain Structure and Its Impact on Magnetic and Transport Properties of Gd_0.6Ca_0.4MnO₃ Thin Films

The evolution of lattice strain on crystallographic domain structures and magnetic properties of epitaxial low-bandwidth manganite Gd0.6Ca0.4MnO3 (GCMO) films have been studied with films on different substrates: SrTiO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrLaAlO3, and MgO. The X-ray diffraction data reveals that all of the films, except the films on MgO, are epitaxial and have an orthorhombic structure. Cross-sectional transmission electron microscopy (TEM) shows lattice mismatch-dependent microstructural defects. Large-enough tensile strain can increase oxygen vacancies concentration near the interface and can induce vacancies in the substrate. In addition, a second phase was observed in the films with tensile strain. However, compressive strain causes dislocations in the interface and a mosaic domain structure. On the other hand, the magnetic properties of the films, including saturation magnetization, coercive field, and transport property depend systematically on the substrate-induced strain. Based on these results, the choice of appropriate substrate is an important key to obtaining high-quality GCMO film, which can affect the functionality of potential device applications

Persistent Luminescence of Tenebrescent Na₈Al₆Si₆O₂₄(Cl,S)₂: Multifunctional Optical Markers

Na₈Al₆Si₆O₂₄(Cl,S)₂ materials were prepared with a solid state reaction. The products were studied using X-ray powder diffraction, reflectance measurements as well as X-ray fluorescence, conventional and persistent luminescence, nuclear magnetic resonance, and electron paramagnetic resonance spectroscopies. All materials containing sulfur showed purple tenebrescence, which persisted 2 days in a lit room at room temperature. Considerable blue persistent luminescence peaking at 460 nm and lasting for 1 h was obtained, as well. Persistent luminescence was obtained with irradiation at 365 nm, while tenebrescence required 254 nm. The materials show great promise as low-cost multifunctional optical markers

Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical

The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with <i>N</i>,<i>N</i>′-bis­(3,5-di-<i>tert</i>-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H₄N₂O₂) are reported. A formally molybdenum­(VI) complex [Mo­(N₂O₂)­Cl₂(dmf)] (<b>1</b>) was synthesized by the reaction between [MoO₂Cl₂(dmf)₂] and H₄N₂O₂, whereas the other molybdenum­(VI) complex [Mo­(N₂O₂)­(HN₂O₂)] (<b>2</b>) was formed when [MoO₂(acac)₂] was used as a molybdenum source. Both complexes represent a rare case of the Mo^VI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations indicate that complex <b>2</b> is the first stable molybdenum­(VI) amidophenoxide radical

Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical

The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with N,N′-bis­(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H4N2O2) are reported. A formally molybdenum­(VI) complex [Mo­(N2O2)­Cl2(dmf)] (1) was synthesized by the reaction between [MoO2Cl2(dmf)2] and H4N2O2, whereas the other molybdenum­(VI) complex [Mo­(N2O2)­(HN2O2)] (2) was formed when [MoO2(acac)2] was used as a molybdenum source. Both complexes represent a rare case of the MoVI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations indicate that complex 2 is the first stable molybdenum­(VI) amidophenoxide radical

Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical

The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with <i>N</i>,<i>N</i>′-bis­(3,5-di-<i>tert</i>-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H₄N₂O₂) are reported. A formally molybdenum­(VI) complex [Mo­(N₂O₂)­Cl₂(dmf)] (<b>1</b>) was synthesized by the reaction between [MoO₂Cl₂(dmf)₂] and H₄N₂O₂, whereas the other molybdenum­(VI) complex [Mo­(N₂O₂)­(HN₂O₂)] (<b>2</b>) was formed when [MoO₂(acac)₂] was used as a molybdenum source. Both complexes represent a rare case of the Mo^VI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations indicate that complex <b>2</b> is the first stable molybdenum­(VI) amidophenoxide radical

Hydrothermal Synthesis of Ni₃TeO₆ and Cu₃TeO₆ Nanostructures for Magnetic and Photoconductivity Applications

Despite great attention toward transition metal tellurates especially M3TeO6 (M = transition metal) in magnetoelectric applications, control on single phasic morphology-oriented growth of these tellurates at the nanoscale is still missing. Herein, a hydrothermal synthesis is performed to synthesize single-phased nanocrystals of two metal tellurates, i.e., Ni3TeO6 (NTO with average particle size ∼37 nm) and Cu3TeO6 (CTO ∼ 140 nm), using NaOH as an additive. This method favors the synthesis of pure NTO and CTO nanoparticles without the incorporation of Na at pH = 7 in MTO crystal structures such as Na2M2TeO6, as it happens in conventional synthesis approaches such as solid-state reaction and/or coprecipitation. Systematic characterization techniques utilizing in-house and synchrotron-based characterization methods for the morphological, structural, electronic, magnetic, and photoconductivity properties of nanomaterials showed the absence of Na in individual particulate single-phase MTO nanocrystals. Prepared MTO nanocrystals also exhibit slightly higher antiferromagnetic interactions (e.g., TN-NTO = 57 K and TN-CTO = 68 K) compared to previously reported MTO single crystals. Interestingly, NTO and CTO show not only a semiconducting nature but also photoconductivity. The proposed design scheme opens the door to any metal tellurates for controllable synthesis toward different applications. Moreover, the photoconductivity results of MTO nanomaterials prepared serve as a preliminary proof of concept for potential application as photodetectors

Role of the Deposition Distance on Nanorod Growth and Flux Pinning in BaZrO₃‑Doped YBa₂Cu₃O_6+<i>x</i> Thin Films: Implications for Superconducting Tapes

A complex deposition process of high-temperature superconducting (HTS) thin films and coated conductors is usually optimized by concentrating on the crystalline quality of the material, thus getting the best possible critical temperature and self-field properties. However, most of the HTS power applications that are based on coated conductors act at high magnetic fields, and thus an alternative approach focusing on the formation of an optimal network of columnar flux pinning centers is more reasonable. Therefore, we systematically show how a lengthening of the deposition distance produces perfectly aligned and distinctly longer self-assembled BaZrO3 (BZO) nanorods within the YBa2Cu3O6+x (YBCO) matrix. This method unambiguously enhances in-field properties such as pinning force, critical current density, and its isotropy along the YBCO c axis. The experimental results, especially formation of the c peak where the relative length of the nanorod is a key issue, are confirmed by the vortex dynamics simulations. Finally, we present a semiquantitative model governing the formation of nanorods that explains the experimentally observed improved nanorod growth as a function of the deposition distance via the associated variation of the fractional partial pressure between atomic species within the laser plume

Hydrodeoxygenation of Isoeugenol over Ni- and Co-Supported Catalysts

Hydrodeoxygenation (HDO) of isoeugenol was investigated over several Ni (Ni/SiO2, Ni/graphite) and Co (Co/SBA-15, Co/SiO2, Co/TiO2, Co/Al2O3) catalysts at 200 and 300 °C under 30 bar hydrogen pressure in a batch reactor. The catalysts were prepared by an impregnation method and systematically characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersive analysis, organic elemental, and thermogravimetrical analysis before and after the reaction. Analysis of the liquid, solid, and gaseous products was performed to identify isoeugenol transformation pathways. The maximum yield of the desired propylcyclohexane (PCH) (63%) and the highest sum of masses of reactants and products in the liquid phase based on GC results (GCLPA) (79%) were obtained over 10 wt % Co/SBA-15. HDO of isoeugenol over 11 wt % Co/SiO2 resulted in 50% PCH yield with a rather similar GCLPA of 73%. Low yields of PCH and the liquid phase mass balance closure were obtained over highly dispersed 15 wt % Co/Al2O3 and 15 wt % Co/TiO2. PCH yield was 60% over Ni/graphite and 44% over Ni/SiO2 after 4 h with GCLPA values of 73 and 70%, correspondingly. Overall PCH yields increased in the following order: Co/TiO2 2O3 2 2 < Ni/graphite < Co/SBA-15. Regeneration and reuse of industrially relevant 11 wt % Co/SiO2 was successfully demonstrated

Strongly Enhanced Growth of High-Temperature Superconducting Films on an Advanced Metallic Template

We demonstrate a straightforward and easily applied technique for growing BaZrO3 doped YBa2Cu3O6+x films of highly improved quality on a commercially used buffered metallic template by pulsed laser deposition. Our method relies on reducing the grain size of the target material, which completely prevents the transfer of the harmful grain boundaries or weak links from the substrate through the buffer layers on the deposited film. We have also observed a great improvement in the self-assembly of BaZrO3 dopants, and the critical current density is increased in the high temperature range up to 40%. As an extra benefit, our method allows us to increasing the growth rate of the film by 25%. We have discussed the results comprehensively and provided quantitative insight into the underlying mechanisms. The presented technique can be considered a groundbreaking advancement for the vastly growing coated conductor industry

Toward Versatile Sr₂FeMoO₆‑Based Spintronics by Exploiting Nanoscale Defects

To actualize the high spintronic application potential of complex magnetic oxides, it is essential to fabricate these materials as thin films with the best possible magnetic and electrical properties. Sr₂FeMoO₆ is an outstanding candidate for such applications, but presently no thin film synthesis route, which would preserve the magnetic properties of bulk Sr₂FeMoO₆, is currently known. In order to address this problem, we present a comprehensive experimental and theoretical study where we link the magnetic and half metallic properties of Sr₂FeMoO₆ thin films to lattice strain, FeMo antisite disorder and oxygen vacancies. We find the intrinsic effect of strain on the magnetic properties to be very small, but also that an increased strain will significantly stabilize the Sr₂FeMoO₆ lattice against the formation of antisite disorder and oxygen vacancies. These defects, on the other hand, are recognized to drastically influence the magnetism of Sr₂FeMoO₆ in a nonlinear manner. On the basis of the findings, we propose strain manipulation and reductive annealing as optimization pathways for improving the spintronic functionality of Sr₂FeMoO₆