1. Condensed-Matter Physics & Materials Science Seminar

    "Oxygen-reduction and Ce-doping effects on the spin excitations in T'-structured Pr1.4-xLa0.6CexCuO4"

    Presented by Masaki Fujita, Institute for Materials Research, Tohoku University, Japan

    Tuesday, June 11, 2013, 1:30 pm
    Small Seminar Room, Bldg. 510

    Hosted by: John Tranquada

    For the emergence of superconductivity in the electron-doped cuprate oxide, both substitution of cation such as Ce4+ at a rear-earth (R) site and annealing procedure under oxygen reduction condition are required. Although the magnetism is recognized to play a key role in the mechanism of superconductivity, the effects of oxygen-reduction and Ce-doping on the spin correlation are not fully understood. In order to extract above two effects on the magnetism, we carried out high-energy inelastic neutron scattering measurements on the as-grown and the Ar-annealed Pr1.40La0.60CuO4-, and as-grown Pr1.32La0.60Ce0.08CuO4. All samples exhibit long-range antiferromagnetic (AF) order at low temperature. The dynamic spin response below ~300 meV throughout the first Brillouin zone was successfully determined. The dispersion relations in both as-grown and annealed Pr1.40La0.60CuO4 are reproduced by the two-dimensional spin-wave relation with the nearest neighbor exchange coupling J of 140±3 meV. However, in the as-grown mother compound, the absolute value of the neutron scattering intensity over the energy range determined in the present study is smaller than that in T-La2CuO4 and ~60% of total inelastic intensity below 250 meV is suppressed by annealing. On the other hand, the zone boundary energy becomes larger by Ce-doping, while the intensity dose not change so much. The origin of anomalous reduction of intensity after annealing is discussed in terms of change in the spin density cloud in the real space.