Microwave Measurements of Pinning Properties in Chemically Deposited YBCO/BZO Films

We present a comparative study of vortex pinning in chemically deposited YBa
₂
Cu
₃
O
_7-x
/BaZrO
₃
nanocomposite films, with the aim of correlating the preparation method to the superconducting properties. Two sets of samples have been prepared by different low fluorine routes (one set followed the in situ approach), with different starting YBCO coating solution and with a different amount of BaZrO
₃
. The short-range vortex pinning properties have been assessed using a contactless microwave (48 GHz) technique, which yielded the vortex pinning constant (Labusch parameter) k
_p
and the vortex viscosity θ as a function of the applied field up to 0.8 T, and for temperatures between 60 K and T
_c
. The results were compared to more usual (long-range vortex motion) J
_c
measurements. Despite the supposed similarity in pinning as determined from J
_c
, we found significant differences between the pinning properties of the two sets of samples. It appears that the in situ approach results in stronger pinning at microwaves in the whole temperature range explored, and that this behavior is due to the smaller dimensions of BaZrO
₃
nanoparticles. This information can be very useful in the search of optimized chemical route to strong pinning superconducting nanocomposite materials.