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Sirena, M., E. Kaul, M. B. Pedreros, C. A. Rodriguez, J. Guimpel, and L. B. Steren. "Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers." Journal of Applied Physics 109, no. 12 (2011): 123920.
Abstract: The La0.75Sr0.25MnO3 (LSMO)/Ba0.7Sr0.3TiO3 (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample’s magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions.
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Navarro, H., I. Yang, M. Sirena, J. Kim, and N. Haberkorn. Characterization of the insulator barrier and the superconducting transition temperature in GdBa2Cu3O7−δ/BaTiO3 bilayers for application in tunnel junctions. Vol. 118., 2015.
Abstract: The optimization of the superconducting properties in a bottom electrode and the quality of an insulator barrier are the first steps in the development of superconductor/insulator/superconductor tunnel junctions. Here, we study the quality of a BaTiO3 tunnel barrier deposited on a 16 nm thick GdBa2Cu3O7−δ thin film by using conductive atomic force microscopy. We find that the tunnel current is systematically reduced (for equal applied voltage) by increasing the BaTiO3 barrier thickness between 1.6 and 4 nm. The BaTiO3 layers present an energy barrier of ≈1.2 eV and an attenuation length of 0.35–0.5 nm (depending on the applied voltage). The GdBa2Cu3O7−δ electrode is totally covered by a BaTiO3 thickness above 3 nm. The presence of ferroelectricity was verified by piezoresponse force microscopy for a 4 nm thick BaTiO3 top layer. The superconducting transition temperature of the bilayers is systematically suppressed by increasing the BaTiO3 thickness. This fact can be associated with stress at the interface and a reduction of the orthorhombicity of the GdBa2Cu3O7−δ. The reduction in the orthorhombicity is expected by considering the interface mismatch and it can also be affected by reduced oxygen stoichiometry (poor oxygen diffusion across the BaTiO3 barrier).
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Ogando, K., and H. Pastoriza. "Design of integration-ready metasurface-based infrared absorbers." Journal of Applied Physics 118, no. 4 (2015): 043109.
Abstract: We introduce an integration ready design of metamaterial infrared absorber, highly compatible with many kinds of fabrication processes. We present the results of an exhaustive experimental characterization, including an analysis of the effects of single meta-atom geometrical parameters and collective arrangement. We confront the results with the theoretical interpretations proposed in the literature. Based on the results, we develop a set of practical design rules for metamaterial absorbers in the infrared region.
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Bauer, E., R. Hauser, A. Galatanu, A. Lindbaum, G. Hilscher, H. Sassik, H. Kirchmayr, J. G. Sereni, and P. Rogl. "New phase boundary between magnetic and non-Fermi-liquid in Ce(Rh1-xRux)(3)B-2, for 0 <= x <= 0.4." Journal of Applied Physics 83, no. 11 (1998): 6423–6425.
Abstract: A study of the temperature-dependent magnetic susceptibility and electrical resistivity rho(T) (0.5-300 K) on single-phase alloys (CaCu5 type), prepared by argon are melting, reveals a magnetic phase transition with a nonmonotonous decrease of the ordering temperature from T-c = 115 K for x = 0 to T-c approximate to 0 for x = 0.40. A kink in the susceptibility at about 70 K indicates that ferromagnetism (at x < 0.1) transforms to a complex magnetic order for 0.125 less than or equal to x less than or equal to 0.35. Above that concentration rho(T) = rho(0) + AT(n) changes from n approximate to 2 to n approximate to 1.5, a characteristic for non-Fermi-liquid behavior. Under pressure T-c stays almost constant for x = 0.125 but dT(c)/dp grows with increasing Ru content. On the contrary, applied fields up to 12 T do not affect T-c. Low-temperature specific heat and ac susceptibility for x = 0.40 confirm the absence of long-range magnetic order down to 0.5 K, For x = 0.35 C-p/T = 62 mJ/mol K at 1.5 K, a value which is three times larger than that of CeRh3B2. (C) 1998 American Insitute of Physics. [S0021-8979(98)46511-3].
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Sereni, J. G., and P. Schlottmann. "Tb impurities in Th: A Kondo system with undercompensated magnetic moment?" Journal of Applied Physics 79, no. 8 (1996): 6417–6419.
Abstract: Dilute TbxTh1-x alloys have been thoroughly studied in the light of a possible valence instability and Kondo effect in Tb3+ and Tb4+ ions. We review the experimental data for the specific heat, magnetic susceptibility, magnetization, magnetoresistivity, and the change of the superconducting properties of Th. In analogy to Tm (Tm2+ and Tm3+) and Pr (Pr3+ and Pr4+) impurities in metals, Tb involves two electronic configurations each with a magnetic Hund's rule ground multiplet. Two classes of models for valence admixtures of two magnetic configurations have been investigated in the past. Depending on the form of the hybridization and the jj coupling within the 4f shell, the models either have a singlet or a magnetic ground state. As for Tm impurities the latter class of models, related to the undercompensated Kondo effect, appears to describe the system TbTh more appropriately A qualitative explanation of the data is attempted within a scheme that combines Kondo screening with crystalline field splitting.
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El-Khatib, S., A. M. Alsmadi, V. Correa, A. V. Andreev, A. Lacerda, F. Nasreen, and H. Nakotte. "Electronic properties of single crystalline UNi[sub 0.39]Rh[sub 0.61]Al." Journal of Applied Physics 103, no. 7 (2008): 07B714–3.
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Osquiguil, E., L. Tosi, E. E. Kaul, and C. A. Balseiro. "On the origin of the low temperatures resistivity minimum in Cr thin films." Journal Of Applied Physics 114, no. 24 (2013): 7 pp.
Abstract: We present measurements of the electrical resistivity and Hall coefficient, p and R-H, in Cr films of different thicknesses grown on MgO (100) substrates, as a function of temperature T and applied magnetic field H. The results show a low temperature minimum in rho(T), which is thickness dependent. From 40K to 2K, the Hall coefficient is a monotonous increasing function as T is reduced with no particular signature at the temperature T-min, where the minimum develops. We explain the resistivity minimum assuming an imperfect nesting of the Fermi surface leading to small electron and hole pockets. We introduce a phenomenological model which supports this simple physical picture. (C) 2013 AI Publishing LLC.
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