Magnetic relaxation of Nd1.85Ce0.15CuO4-δ single crystal

The vortex dynamics of a Nd1.85Ce0.15CuO4-delta single crystal was investigated in terms of its magnetic relaxation process. The measurement of time dependent magnetization was carried out in a magnetic field of 750 Oe applied parallel to the c-axis with temperature varying from 5 to 17 K, covering the second peak region and extending below as well as above its temperature range. The normalized relaxation rates S determined from the FC and ZFC data generally exhibit asymmetrical behaviours, and both feature narrow and shallow valleys, interrupting the otherwise monotonic rise of the curve. In particular, the ZFC data For S(T) displays an additional maximum somewhat similar to those found in BSCCO and TBCCO. The data are further analyzed on the basis of collective flux creep model. (C) 2000 Elsevier Science B.V. Ail rights reserved.