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Sutter, J. G., A. Sarmiento Chavez, Soria, M. Granada, L. Neñer, S. Bengió, P. Granel, F. Golmar, H. Haberkorn, G. Leyva et al. "Stress and disorder effect in the physical properties of artificially engineered multiferroic superlattices." Materials Chemistry and Physics 271 (2021): 124910.
Abstract: La0·8Ba0·2MnO3, Ba0·25Sr0·75TiO3 and BaTiO3 superlattices were grown to study the influence of structural disorder on the physical properties of multiferroic multilayers. Controlling the lattice mismatch of the superlattices allowed growing structures with different growth mechanisms. The manganite layers in the samples were used as “sensor layers”, that respond to the structural changes in the superlattices, induced by changing the thickness and nature of the ferroelectric layers. Stress has a weak influence on the magnetic properties of these systems. Transport properties are characterized by a high temperature thermally activated regime and a low temperature variable hopping one. The strain and structural disorder in the samples increases the localization energy of the current carriers for both regimes. Important interface effects can be achieved controlling the strain and disorder in the interfaces, allowing tuning the metal-insulator transition temperature. These results help to further understand the role of interface effects in the development of manganite based ferromagnetic/ferroelectric multilayered systems.
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Hofer, J. A., S. Bengio, G. Rozas, P. D. Pérez, M. Sirena, S. Suárez, and N. Haberkorn. "Compositional effects on the electrical properties of extremely disordered molybdenum oxynitrides thin films." Materials Chemistry and Physics 242 (2020): 122075.
Abstract: Molybdenum oxynitride (MoNxOy) thin films were grown by reactive sputtering on Si (100) substrates at room temperature. The partial pressure of Ar was fixed at 90%, and the remaining 10% was adjusted with mixtures N2:O2 (varying from pure N2 to pure O2). The electrical properties of the films depend on the chemical composition. Thin films grown using mixtures up to 2% O2 have γ-Mo2N phase and display superconductivity. The superconducting critical temperature Tc reduces from ∼6.8 K to below 3.0 K as the oxygen increases. On the other hand, the films are mostly amorphous for gas mixtures above 2% O2. The electrical conductivity shows a semiconductor-like behavior well described by variable-range hopping conduction. The analysis of the optical properties reveals that the samples do not have a defined semiconductor bandgap, indicating that the high structural disorder produces electron excitation for a wide range of energies.
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Haberkorn, N., Y. Y. Zhang, Z. X. Bi, B. H. Park, L. Civale, and Q. X. Jia. "Effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer assisted deposition." Materials Chemistry and Physics 259 (2021): 124184.
Abstract: We report the effect of Co2N impurity on the superconducting properties of δ-MoN thin films grown by polymer-assisted deposition on c-cut sapphire (Al2O3). The films show a superconducting transition temperature of 10.4 K and an upper critical field Hc2(0) perpendicular to the film surface around 3 T. The latter corresponds to a relatively large coherence length ξ, which enhances the two-dimensional limit when the magnetic field is applied parallel to the film surface. In comparison with pure δ-MoN films, the inclusion of Co2N impurity in the δ-MoN films could significantly modify the critical current density at the vortex-free state. The ability to tune the superconducting properties of metal-nitride superconductors by introducing chemically and structurally compatible impurity may find potential applications for superconducting single-photon detectors.
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Haberkorn, N., S. Bengio, H. Troiani, S. Suárez, P. D. Pérez, P. Granell, F. Golmar, M. Sirena, and J. Guimpel. "Thickness dependence of the superconducting properties of γ- Mo<inf>2</inf>N thin films on Si (001) grown by DC sputtering at room temperature." Materials Chemistry and Physics 204 (2018): 48–57.
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Gil, D. M., G. Nieva, D. G. Franco, M. I. Gómez, and R. E. Carbonio. "Lead nitroprusside: A new precursor for the synthesis of the multiferroic Pb2Fe2O5, an anion-deficient perovskite." Materials Chemistry and Physics 141, no. 1 (2013): 355–361.
Abstract: In order to investigate the formation of multiferroic oxide Pb2Fe2O5, the thermal decomposition of Pb[Fe(CN)5NO] has been studied. The complex precursor and the thermal decomposition products were characterized by IR and Raman spectroscopy, thermal analysis, powder X-ray diffraction (PXRD), scanning electron microscopy and magnetic measurements. The crystal structure of Pb[Fe(CN)5NO] was refined by Rietveld analysis. It crystallizes in the orthorhombic system, space group Pnma. The thermal decomposition in air produces highly pure Pb2Fe2O5 as final product. This oxide is an anion deficient perovskite with an incommensurate superstructure. The magnetic measurements confirm that Pb2Fe2O5 shows a weak ferromagnetic signal probably due to disorder in the perfect antiferromagnetic structure or spin canting. The estimated ordering temperature from the fit of a phenomenological model was 520Â K. The SEM images reveal that the thermal decomposition of Pb[Fe(CN)5NO] produces Pb2Fe2O5 with small particle size.
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Domenichini, P., Condó, A. M., Haberkorn, N. "Structural characterization of FeePd nanowires grown by electrodeposition using an acid electrolyte." Materials Chemistry and Physics 177 (2016): 164–170.
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