Effects of Zr Doping on Magnetic and Structural Properties of DyBa2Cu3O $_{7-\delta }$ Thin Films

DyBa
₂
(Cu
_1-x
-Zr
_x
)
₃
O
_7-δ
thin films (with x = 0.00, 0.02, 0.04, and 0.06) were synthetized using the chemical solution deposition method on single crystalline LaAlO
₃
substrates. Effects resulting from Zr doping were investigated by means of magnetic and structural measurements. X-ray diffraction analysis demonstrated a strong c-axis orientation in the DyBa
₂
(Cu
_1-x
Zr
_x
)
₃
O
_7-δ
thin films, with only minor reflections due to the presence of Dy
₂
O
₃
and BaZrO
₃
phases. Narrow transitions with ΔTc ranging from 1 to 2 K for samples with x = 0.00 and 0.06, respectively, were observed in ac magnetic susceptibility curves, where the nondoped sample demonstrated the highest T
_c
^onset
of 91.7 K compared to the Zr-doped samples. Critical current densities J
_c
of the thin films were obtained from magnetization loop measurements with applied magnetic fields up to 6 T and by employing the Bean model. The sampled doped with 4% Zr exhibited the highest J
_c
value (J
_c
= 3.5 MA/cm
²
, self-field, 77 K) in the low field range and we, in general, observed that Zr-doped films demonstrated higher values compared to the pure sample. Pinning force plots (F
_p
versus B) reveal a significant improvement over the magnetic field range investigated of the maximum pinning force for Zr-doped samples. We found F
_p
^Max
= 1.7 GN/m
³
and 3.8 GN/m
³
for pure and 6% Zr samples, respectively. Analysis based on the Dew-Hughes model shows that normal surface pinning is the dominating pinning mechanism.