Temperature dependence of activation energy due to intrinsic pinning for flux lines in (Nd1−xCex)2CuO4−δfilms

Using electron superconductor (Nd1−xCex)2CuO4−δfilms prepared by a laser ablation technique, we measured the temperature dependence of the resistivity in magnetic fields and the magnetic field-direction dependence of the critical current. The temperature dependence of the resistivity in magnetic fields was analyzed using an activation type of formula. The temperature dependence of the activation energy for some oxide superconductors for H∥ the basal plane was calculated using the intrinsic pinning model proposed by Tachiki and Takahashi. The temperature dependence changed systematically depending on the ratio of the coherence length along the c-axis to the inter-distance between CuO conductive planes. The magnetic field-direction dependence of the critical current was also explained using the model. From these analyses, the origin of the temperature dependence of the activation energy is discussed.