石井 涼太

Abstract We fabricated GdBa₂Cu₃O_7-δ (Gd123) superconducting thin films on LaAlO₃ single-crystal substrates using the FF-MOD method. The superconducting properties of thin films doped with various volume fractions of Gd₂CuO_4-x (Gd214) as new type of artificial pinning centers (APCs) were evaluated. As a result, we successfully introduced up to 5.95vol% of the c-axis oriented Gd214 into Gd123 films. The maximum J _C at 4.2 K was observed in the film doped with 1.98vol% Gd214, reaching 3.05 MA/cm² at 3.0 T and 2.00 MA/cm² at 6.9 T, which are 2.21 times and 2.75 times higher than those of the non-doped film, respectively. Building on these results, we attempted to introduce various types of RE ₂CuO_4-x (RE214: RE= Gd, Sm, Nd) microcrystals as APCs and investigated their superconducting properties. The findings revealed that lattice matching between the c-axis lattice constants of the base material and the pinning material is critical to improve J _C-B properties.

Abstract We have fabricated BaCeO₃ (BCO) and Gd₂CuO₄ (Gd214) co-doped GdBa₂Cu₃O_7-δ thin films on LaAlO₃ single crystal substrates by fluorine-free metal organic deposition method and investigated their crystallinity and superconducting properties. The J _C-B properties of the co-doped film were improved compared to those of films with single Gd214 or BCO doped films at the same volume fraction, respectively. 2vol% Gd214 and 1vol% BCO co-doped film showed the maximum J _C of 5.92 MA/cm² (4.2 K, B//c, B=1 T) and 0.24 MA/cm² (77.3 K, B//c, B=1 T). These values were 1.89 and 1.85 times higher than those of the 3vol% single Gd214 doped film, respectively.