Effects of Pb(Zr_0.52Ti_0.48)O₃ polarization on the YBa₂Cu₃O_{7− x} electrical transport and magnetization

The YBa₂Cu₃O_{7− x} (YBCO) superconducting film of 70 nm thickness was prepared on a LaAlO₃ (LAO) substrate via the sol–gel method, following which the Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric film possessing interfacial coherent structure was grown via pulsed laser deposition (PLD) method, and then the Pt top electrode was deposited onto the PZT film by DC sputtering, resulting in the Pt/PZT/YBCO tri-layer structure. The ferroelectric hysteresis characteristics and the effects of ferroelectric polarization field of PZT on the electrical properties and magnetization of YBCO were studied for the temperature range of 50–300 K. Results reveal that as the temperature decreases, the remanent polarization of Pt/PZT/YBCO remains nearly constant, while the coercive field increased. The R–T curve of YBCO shifts upwards (positive polarization) or downwards (negative polarization) due to the influence of PZT polarization, indicating that the ferroelectric polarization of PZT modulates the R–T curve of YBCO. When YBCO is in the superconducting state, the magnetization of YBCO decreases with increasing polarization of PZT, indicating that the polarization field of PZT has a modulation effect on the magnetization of YBCO. Further investigation on the J–V curve of Pt/PZT/YBCO revealed a threshold conduction voltage ( V _t) and when the applied bias voltage was lower than V _t, the leakage current of Pt/PZT/YBCO was small, and when the applied voltage was higher than V _t, the leakage current rapidly increased. Meanwhile, the V _t increased with decreasing temperature and then markedly changes at the superconducting transition temperature of YBCO. (paper)