86,687 research outputs found

    First order nucleation of charge ordered domains in La0.5Ca0.5MnO3 detected by 139La and 55Mn NMR

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    The local magnetism and charge ordering of La0.5Ca0.5MnO3, was investigated between room temperature and 1.3 K by means of La-139 and Mn-55 NMR. Antiferromagnetic and ferromagnetic domains are assigned unambiguously to the insulating charge ordered and the metallic state respectively. The phases are found to coexist at all temperatures below the first formation of a charge-ordered state. The two signal fractions display thermal and magnetic hysteresis, while their local fields and relaxations do not. These features and the absence of any critical behavior are characteristic of a first order F-AF transition, with ferromagnetic domains microscopically identical to the bulk metallic phase of the OM

    Modelling of the reactive interface formation on Bi2Sr2CaCu2O8

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    We have applied the phenomenological model of diffused interfaces, developed originally to describe the Fe growth on Bi2Sr2CaCu2O8, to interpret quantitatively the core photoemission spectra of two reactive interfaces, namely Cr and Ge on Bi2Sr2CaCu2O8. At room temperature the interfaces with Fe and Cr have the same kinetics of growth suggesting similar adatom condensation, while the semiconductor-superconductor interface grows layer-by-layer according to the Franck-van der Merwe kinetics. Differences in the parameters of the model resulting from the simultaneous fit of the core-level decays are related to differences in the microscopic processes occurring during the growth

    Tunneling spectroscopy of Fe-doped YBa2Cu3O7 single crystals

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    A comparison between the orthorhombic oxygen-deficient YBa2Cu3O7-Î ́ 60-K phase and the tetragonal YBa2(Cu0.96Fe0.04)3O7 system with Tc=57 K is made by means of tunnel junctions. No relevant differences are found in the behavior of the high-voltage gaplike structure at 25 mV while a suppression of the low-voltage structure at 5 mV is observed in the Fe-doped junctions. In some cases a zero-bias conductance peak is developed; this anomaly is analyzed in the framework of the Appelbaum-Kondo model for electron magnetic interactions. © 1992 The American Physical Society
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