JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, vol.25, no.2, pp.267-271, 2012 (SCI-Expanded)
We have studied magnetization anisotropy in a YBa2Cu3O7 sample synthesized by a modified melt powder melt growth (MPMG) method. Magnetization of the sample upon ZFC process was measured as a function of magnetic field oriented both parallel and perpendicular to the c-axis. Magnetization anisotropy parameter gamma is determined from remanent magnetization as a function of temperature. Magnetic relaxation measurement has been carried out in selected magnetic fields in both field increasing and decreasing case. At 20 kOe and 25 K for the field increasing case, the activation energy was found to be 53.5 meV and 51.7 meV when Hayenc and HaSyenc, respectively. Calculations based on the critical-state model can reproduce quite well the experimental data for Hayenc and HaSyenc where we have chosen n=0.15 and n=0.3, respectively.