Fishtail effect, magnetic properties and critical current density of Gd-added PMP YBCO

The magnetization curves of YBa2Cu3Oy and Y0.4Gd0.6Ba2Cu3Oy samples prepared by a powder melting process technique were measured with a superconducting quantum interference device magnetometer at different temperatures. Fishtail effects are observed below 70 K with the H perpendicular to c configuration in the Gd-added sample, while no peak effect is found in YBCO. The origin of the fishtail is discussed. It is found that J(c) and flux pinning can be increased by the Gd addition. The magnitude of the improvement of J(c) increases with the magnetic field. The reduction of the size of Y2BaCuO5 particles, stress-field pinning and magnetic pinning induced by the substitution of Gd for Y may explain the enhancement of J(c) and flux pinning. (C) 1998 Elsevier Science B.V.