In-field superconducting critical current of Y0.5Gd0.5Ba2Cu3O7-σ films obtained by a multi-step deposition process

For most applications of high-temperature superconducting tapes, a high critical current (Ic) and critical current density (Jc) under a magnetic field are both required. The simplest way to achieve high Ic is to increase the thickness of the superconducting layer. However, doing so also reduces Jc, which is called the thickness effect. In this work, to inhibit the thickness effect, a series of Y0.5Gd0.5Ba2Cu3O7-σ (YGBCO) films with different thicknesses (240-1200 nm) were deposited by multi-step pulsed laser deposition on cerium oxide (CeO2) buffered substrates. The thickness dependence of the in-field Jc was systematically investigated. The in-field Ic at 77 K and 0-0.5 T was measured using the four-probe method, the surface morphology was observed using scanning electron microscopy, the structure and texture were measured using X-ray diffraction, and the internal residual stress was evaluated using the Williamson-Hall method. It was found that Jc first increased and then decreased with increasing YGBCO film thickness. The 480-nm YGBCO film had the highest Jc of 4.33 MA/cm2 at 77 K and a self-field>1.5 MA/cm2 under a magnetic field of 0.5 T. A 720-nm YGBCO film showed the slowest rate of Jc degradation under a magnetic field. The experimental results are discussed by considering the deposition process and growth model.