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Pressure Dependence of the Magneto-transport Properties in Fe/MgO Granular Systems
A. Garc´ıa-Garc´ıa,P. A. Algarabel,J. A. Pardo,Z. Arnold,J. Kamarad 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10
The effect of hydrostatic pressure at room temperature on the resistance and magnetoresistance (MR) of a discontinuous metal-insulator multilayer (DMIM) of nominal composition [Fe(tFe = 0.7nm)/MgO(tMgO = 3 nm)]15 has been studied. The resistivity of the DMIM, ρ, decreases linearly with pressure indicating an increase in conduction via tunneling effect. The value of coefficient (1/ρ0)dρ/dP = –3.9 × 10−2 kbar−1 is higher than reported values in other granular films implying that the electronic state of the DMIM is close to the iron percolation threshold. At the maximum applied magnetic field (3 kOe) the MR ratio increases from 0.6% at ambient pressure to 1.1% at 7 kbar. This result can be explained by a reduction of the tunnel barrier width induced by the hydrostatic pressure.
Ground State and the Metal-insulator Transition in (Pr1−yYy)1−xCaxCoO3 (0.45 ≤ x ≤ 0.55) Cobaltites
A. J. Bar´on-Gonz´alez,J. L. Garc´ıa-Mu˜noz,J. Herrero-Mart´ın,C. Frontera,G. Sub´ıas,J. Blasco 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Pr0.5Ca0.5CoO3 exhibits a non-conventional metal-insulator transition (MIT) in which the insulatingstate is due toa volume contraction (2%) and electron transfer from Pr to Co sites. Pr1−xCaxCoO3cobaltites with Ca doping around x 0.5 (0.45 ≤ x ≤ 0.55) have been investigated. Different ground states and phase transitions are reported in samples at both sides of the half-dopedcomposition. The relevance of the Pr/Ca ratio around half-doping and the amplitude of the changesobserved at the MIT are analyzed. Besides the expected variation in the transition temperature, wereport an enhanced Pr3+/Pr4+ transformation at the MIT in Pr0.45Y0.05Ca0.50CoO3[0.25(5) e−/Pr ion and TMI = 120 K] with respect to Pr0.5Ca0.5CoO3[0.15(5) e−/ Pr ion and TMI = 75 K].
Structural and Optical Properties of Hydrothermally-synthesized Single-crystalline Sb2O3 Nanowires
N. M. A. Hadia,Santiago Garc´ıa-Granda,Jos´e R. Garc´ıa 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.11
Antimony-trioxide (Sb2O3) nanowires were synthesized by using the hydrothermal method. Theproducts were characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy,scan electron microscopy, energy dispersive spectroscopy and transmission electron microscopy(TEM). The products were found to be orthorhombic, crystalline nanowires of Sb2O3 with diametersof 65-85 nm and lengths up to several micrometers. Selected area electron diffraction andhigh-resolution TEM studies indicated the single-crystalline nature of the Sb2O3 nanowires withan oriented growth along the [001] direction. The absorption spectrum of the as-prepared Sb2O3nanowires showed an absorption peak around 361 nm. These Sb2O3 nanowires exhibited bright photoluminescencewith a strong emission band at 395 nm. The as-synthesized Sb2O3 nanowires areexpected be new functional materials and to be used in the manufacture of advanced optoelectronicnanodevices.