Flux Pinning Characteristics of ${\rm Sm}_{1+x}{\rm Ba}_{2-x}{\rm Cu}_{3}{\rm O}_{y}$ Films With the Additional $c$-Axis Correlated Pinning Centers

It is known that columnar defects comprised of self-organized BaZrO
₃
(BZO) nanorods within REBa
₂
Cu
₃
O
y
(REBCO) films are attractive as
c
-axis correlated pinning centers. On the other hand, we have fabricated high-J
_c
Sm
_1+x
Ba
_2-x
Cu
₃
O
_y
(SmBCO) films including nanosized low-T
_c
phases 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 the
c
-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 the
c
-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.