Search

Josephson vortices in Bi2Sr2CaCu2O8+δ single crystals have been studied to measure the vortex-flow resistance with the current perpendicular to the superconducting layers, sweeping the parallel magnetic fields. In the flow resistance, we have found novel periodic oscillations. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. It is considered that the oscillations take place with a coherent motion of the vortices in the dynamical flow. These results suggest that the Josephson vortices form a triangular lattice in the ground state, related to the matching effect between the sample width and the lattice spacing along the layers. It is also suggested that they will be applicable to a new type of magnetic sensor. [Copyright &y& Elsevier]

We have measured the Josephson vortex flow resistance with the current perpendicular to the Cu–O layers of Bi2Sr2CaCu2O8+δ. It has been found that novel periodic oscillations appear in the flow resistance with sweeping the magnetic field parallel to the layers. The oscillations have been observed in a wide range of parallel fields larger than 6 kOe and only in a smaller current density than about 100 A/cm2. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. These results suggest that the Josephson vortices form a triangular lattice as a ground state. [Copyright &y& Elsevier]

We have measured the Josephson vortex flow resistance with the current perpendicular to the Cu–O layers of Bi2Sr2CaCu2O8+δ. It has been found that novel periodic oscillations appear in the flow resistance with sweeping the magnetic field parallel to the layers. The oscillations have been observed in a wide range of parallel fields larger than 6 kOe and only in a smaller current density than about 100 A/cm2. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. These results suggest that the Josephson vortices form a triangular lattice as a ground state. [ABSTRACT FROM AUTHOR]

In the vortex-flow resistance measured with the current perpendicular to the superconducting layers of Bi2Sr2CaCu2O8+δ, we have found novel periodic oscillations with sweeping the magnetic field parallel to the layers. The oscillations have been observed in a wide range of parallel fields larger than 6 kOe and only in a smaller current region than 200 μA. The period of the oscillations corresponds to adding “one” flux quantum per “two” intrinsic Josephson junctions. These results suggest that the Josephson vortices form a triangular lattice in moving vortices, related to the matching between the sample width and the lattice spacing along the layers, and supply important evidence for new applications. [Copyright &y& Elsevier]

The time decay of the zero field cooled diamagnetic magnetization of Bi2Sr2CaCu2O8 single crystals can be explained in terms of a characteristic relaxation time τ0 and a mean activation energy E which is proportional to the reciprocal magnetic field. We find that τ0 becomes extremely long to be around 10 s at low temperatures below 14 K. This low temperature phase in the vortex solid region is also directly confirmed by the ac susceptibility measurements in the ultra low frequency range. [Copyright &y& Elsevier]

Abstract: Josephson-vortex (JV) states in Bi2Sr2CaCu2O8+y (Bi-2212) have been studied by measuring the flow resistance of JVs and I–V characteristics with a current along the c-axis and a magnetic field parallel to the superconducting layers. In the flow resistance, periodic oscillations have been found as a function of the parallel field. As this phenomenon is related to the formation of a triangular lattice of JVs as the ground state, the 3D-ordered state of JVs can be determined in the magnetic phase diagram. With increasing the doping level of Bi-2212, the 3D-ordered phase is shifted towards a higher magnetic field and a higher temperature, which is well explained by the theoretical analyses. Above the 3D-ordered phase, JV state has been studied with I–V characteristic measurements, in which the voltage shows a distinct change in the exponent of the power-law dependence to the current between two phases. This suggests that the 3D-ordered phase changes to the disordered phase along the c-axis. [Copyright &y& Elsevier]