Superconducting properties in SmBa₂Cu₃O_y films with high density of BaHfO₃ nanorods fabricated with a seed layer

A high density of BaMO₃ (BMO) nanorods within a REBa₂Cu₃O_y (REBCO) film can be generated by heavy doping of the BMO. This is very effective in improving superconducting properties in high magnetic fields. However, heavy doping causes a significant T_c reduction. Introduction of a high density of BMO nanorods into REBCO films without reduction in T_c is required. To this end, we deposited SmBa₂Cu₃O_y (SmBCO) films with various amount of BaHfO₃ (BHO) by a pulsed laser deposition (PLD) method using a seed-layer technique and a low-temperature growth (LTG) technique. Using this technique, we can fabricate a purely c-axis-oriented SmBCO film even at low substrate temperatures T_s. The SmBCO films with BHO were fabricated at low T_s of 750 °C without heavy doping of BHO. As a result, the BHO nanorods became thinner and denser than those within SmBCO films fabricated by conventional PLD methods at high T_s. The maximum density was 4780/μm², and the B_phi of the film reached 9.9 T. These samples showed high T_c (> 90 K). We have therefore successfully fabricated high-T_c SmBCO films with high densities of BHO nanorods using the LTG technique.