Superconducting anisotropy in Nd1.85Ce0.15CuO4 single crystals

The magnetic torque of the Nd1.85Ce0.15CuO4 crystal consists of three contr ibutions in the superconducting state, i.e., (1) a torque of the anisotropi c magnetic moment of the Nd3+ ions, (2) a torque coming from the mass diffe rence between m(ab), and m(c) and (3) a torque of the vortex lock-in states appeared when the field is applied parallel to the CuO2 planes. We analyze a torque component arising from the mass anisotropy by using the anisotrop ic London model and obtain an anisotropy parameter gamma (c) = 28 +/- 3. Th e irreversibility line of Nd1.85Ce0.15CuO4 is in excellent accordance with that of the La-based cuprate. (C) 2001 Elsevier Science B.V. All rights res erved.