Spin-Glass-like Transition and Hall Resistivity of Y2-xBixIr2O7

Various physical properties of the pyrochlore oxide Y2-xBixIr2O7 have been studied. The magnetizations M measured under the conditions of the zero-field-cooling(ZFC) and the field-cooling(FC) have different values below the temperature T=TG. The anomalous T-dependence of the electrical resistivities r and the thermoelectric powers S observed at around TG indicates that the behavior of the magnetization is due to the transition to the state with the spin freezing. In this spin-frozen state, the Hall resistivities rH measured with the ZFC and FC conditions are found to have different values, too, in the low temperature phase (T<TG). Possible mechanisms which induce such the hysteretic behavior are discussed.Comment: 9 pages, 7 figures, J. Phys. Soc. Jpn. 72 (2003) No.

Torsion-induced persistent current in a twisted quantum ring

We describe the effects of geometric torsion on the coherent motion of electrons along a thin twisted quantum ring. The geometric torsion inherent in the quantum ring triggers a quantum phase shift in the electrons' eigenstates, thereby resulting in a torsion-induced persistent current that flows along the twisted quantum ring. The physical conditions required for detecting the current flow are discussed.Comment: 9 pages, 3 figure

High sensitive X-ray films to detect electron showers in 100 GeV region

Nonscreen type X-ray films were used in emulsion chamber experiments to detect high energy showers in cosmic rays. Ranges of the detection threshold is from about 1 to 2 TeV depending on the exposure conditions. Different types of X-ray films and sheets i.e. high sensitive screen type X-ray films and luminescence sheets were tested. The threshold of the shower detection is found to be about 200 GeV, which is much lower than that of nonscreen type X-ray films. These films are useful to detect showers in the medium energy range, a few hundred GeV, of the cosmic ray electrons