8 research outputs found

    Nonlinear paramagnetic magnetization in the mixed state of CeCoIn_5

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    Torque and magnetization measurements in magnetic fields HH up to 14 T were performed on CeCoIn5_5 single crystals. The amplitude of the paramagnetic torque shows an H2.3H^{2.3} dependence in the mixed state and an H2H^{2} dependence in the normal state. In addition, the mixed-state magnetizations for both H∥cH\parallel c and H∥abH\parallel ab axes show anomalous behavior after the subtraction of the corresponding paramagnetic contributions as linear extrapolations of the normal-state magnetization. These experimental results point towards a nonlinear paramagnetic magnetization in the mixed state of CeCoIn5_5, which is a result of the fact that both orbital and Pauli limiting effects dominate in the mixed state.Comment: 2 pages, 2 figures, conferenc

    Magnetotransport Properties of Antiferromagnetic YBa_2Cu_3O_6.25 Single Crystals

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    In-plane and out-of-plane magnetoresistivities (MR) of antiferromagnetic YBa_2Cu_3O_6.25 single crystals were measured in magnetic fields H applied along the (ab) plane. In-plane MR is a superposition of two components: The first component is strongly in-plane anisotropic, changing sign from negative when H is parallel to the electrical current I to positive when H is perpendicular to I. The second component is positive, quadratic in H, and isotropic in the (ab)-plane. The out-of-plane MR displays a fourfold symmetry upon in-plane rotation of the magnetic field, with maxima along the easy axes of antiferromagnetic spin ordering and minima along unfavorable directions of spin orientation (45 degrees from the Cu-O-Cu bonds).Comment: 8 pages, 4 figure

    Universal scaling of the Hall resistivity in MgB2 superconductors

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    The mixed-state Hall resistivity and the longitudinal resistivity in superconducting MgB2 thin films have been investigated as a function of the magnetic field over a wide range of current densities from 100 to 10000 A/cm^2. We observe a universal Hall scaling behavior with a constant exponent of 2.0, which is independent of the magnetic field, the temperature, and the current density. This result can be interpreted well within the context of recent theories.Comment: 4 page

    Theory for Electron-Doped Cuprate Superconductors: d-wave symmetry order parameter

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    Using as a model the Hubbard Hamiltonian we determine various basic properties of electron-doped cuprate superconductors like Nd2−xCexCuO4{Nd}_{2-x}{Ce}_{x}{CuO}_{4} and Pr2−xCexCuO4{Pr}_{2-x}{Ce}_{x}{CuO}_{4} for a spin-fluctuation-induced pairing mechanism. Most importantly we find a narrow range of superconductivity and like for hole-doped cuprates dx2−y2d_{x^{2}-y^{2}} - symmetry for the superconducting order parameter. The superconducting transition temperatures Tc(x)T_{c}(x) for various electron doping concentrations xx are calculated to be much smaller than for hole-doped cuprates due to the different Fermi surface and a flat band well below the Fermi level. Lattice disorder may sensitively distort the symmetry dx2−y2d_{x^{2}-y^{2}} via electron-phonon interaction

    In-plane Hall effect in c-axis-oriented MgB2 thin films

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    We have measured the longitudinal resistivity and the Hall resistivity in the ab-plane of highly c-axis-oriented MgB2 thin films. In the normal state, the Hall coefficient (R_H) behaves as R_H ~ T with increasing temperature (T) up to 130 K and then deviates from that linear T-dependence at higher temperatures. The T^2 dependence of the cotangent of the Hall angle is only observed above 130 K. The mixed-state Hall effect reveals no sign anomaly over a wide range of current densities from 10^2 to 10^4 A/cm^2 and for magnetic fields up to 5 T.Comment: 5 pages including 5 figure
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