Flux Pinning Characteristics of Sm₁₊ₓ Ba₂₋ₓ Cu₃ Oy Films With the Additional c-Axis Correlated Pinning Centers

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It is known that columnar defects comprised of self-organized BaZrO3(BZO) nanorods within REBa2Cu3Oy(REBCO) films are attractive asc-axis correlated pinning centers. On the other hand, we have fabricated high-JcSm1+xBa2-xCu3Oy(SmBCO) films including nanosized low-Tcphases by using the low-temperature growth (LTG) technique. In this study, BZO nanorods were added to the LTG-SmBCO film for a further enhancement of the magnetic flux pinning. Additionally, we also deposited a conventional PLD-SmBCO film including BZO nanorods and discussed differences of the flux pinning properties and microstructures between LTG- and PLD-SmBCO films. In a cross-sectional transmission electron microscopy (TEM) image of the BZO doped PLD-SmBCO film, we could see the self-organized BZO nanorods were about 10 nm in diameter, extending along thec-axis of the film. In contrast, in the BZO doped LTG-SmBCO film, the high density BZO nanorods with smaller diameters tended to be short columns and tilted against thec-axis direction. These facts can be attributed to a suppression of the surface diffusion length of adatoms and/or an increase of nucleation frequency due to the low substrate temperature during the growth of the BZO doped LTG-SmBCO film. Furthermore, we concluded that differences of superconducting properties between the BZO doped PLD- and LTG-SmBCO films might be attributed to the difference in the number density of BZO nanorods which generated lattice strain around them.