Observation of pancake-like vortex in the angular dependence of the magnetization around H‖a-axis in Nd1.858Ce0.142CuO4 single crystal

Angular and magnetic field dependences of the magnetization in the mixed state have been measured on Nd1.858 Ce0.142 CuO4 single crystal. The angular dependence of the magnetization due to the superconductivity in the mixed state shows an anomalous peak just around H‖a-axis above 2 kOe in ZFC and the peak becomes sharp with increasing magnetic fields. The magnetization curve for H‖a-axis shows negligibly small hysteresis in the mixed state between the increase and the decrease of the magnetic fields above 5 kOe. These behaviors were discussed on the basis of the vortex configuration and the superconducting anisotropy of this crystal. If the vortex would be pancake-like and could not exist in the sample for H‖a-axis, the anomalous behaviors could be understood qualitatively. It was concluded that the dimensional crossover from 3-D to 2-D in the vortex system began to occur in H>5 kOe and the pancake-like vortex appeared at higher magnetic fields.