Analysis of angular dependence of pinning mechanisms on Ca-substituted YBa2Cu3O7-δ epitaxial thin films

The critical current density Jc as a function of the temperature T, magnetic field intensity H and angle θ between the direction of applied magnetic field and the c-axis of the samples was measured on epitaxial 10 at.% Ca-substituted YBa2Cu3O7-δ (YCBCO) thin films grown by the pulsed laser deposition technique on (001)-SrTiO3 (STO) and CeO2 buffered r-cut Al2O3 (CAO) substrates. Films exhibited comparable values of critical temperature (Tc∼78 K) while higher self-field Jc values for SrTiO3 were observed. Dissipation regimes related to growth boundary and intra-grain pinning mechanisms showed a qualitatively similar contribution for YCBCO films deposited on both substrates when the applied magnetic field direction is parallel to the c-axis (θ = 00). However, a weaker efficiency of pinning related to growth boundaries as well as a wider field range where this dissipation mechanism is active were observed for films grown on CeO2-buffered sapphire. These films exhibited a broad peak centred at θ = 00 in the Jc versus angle behaviour, not observed using a SrTiO3 substrate. The analysis of the Jc(H) dependences collected at θ = 900 revealed that this feature can be partially ascribed to a dramatic decrease of the intrinsic pinning efficiency