Elaborately designed bilayers consisting of epitaxial ${\text{YBa}}_2{\text{Cu}}_3{\text{O}}_{7-\delta }$ (YBCO) and ${\text{La}}_{0.67}{\text{Sr}}_{0.33}{\text{MnO}}_{3-\delta }$ (LSMO) films were fabricated by pulsed laser deposition with respect to the investigation into magnetic-dependent vortex pinning effect. The improvement in the critical current density and a pronounced upward shift in the superconducting irreversibility line based on magnetotransport measurements are observed when compared to the pure YBCO film, suggesting the enhancement in flux pinning in the studied bilayer. It is believed that the improved flux pinning for YBCO arises from the magnetic inhomogeneity of the underlying LSMO. Magnetization measurements show a nonuniform magnetic state in the LSMO film, most probably being macroscopically phase-separated clusters with ferromagnetic (FM) and anti-FM domains, which can be caused by the epitaxial strain due to the lattice mismatch. Such a magnetic disorder is hardly affected by the external magnetic field, unlike the magnetic disorder induced by the domain structures of FM materials where the magnetic domains naturally disappear as the applied field exceeds the coercive field. Hence, the present magnetic flux pinning may be stiff in the large magnetic fields, showing good prospects for artificial flux pinning enhancements.

Point defect pinning centers are the key factors responsible for the flux pinning and critical current density in type II superconductors. The introduction of the point defects and increasing their density without any changes to the superconducting transition temperature T_c, irreversibility field H_irr, and upper critical field H_c2, would be ideal to gain insight into the intrinsic point-defect-induced pinning mechanism. In this work, we present our investigations on the critical current density J_c, H_c2, H_irr, the activation energy U₀, and the flux pinning mechanism in Fe_1-xCo_xSe_0.5Te_0.5 (x = 0, 0.03 and 0.05) single crystals. Remarkably, we observe that the J_c and U₀ are significantly enhanced by up to 12 times and 4 times for the 3at.% Co-doped sample, whereas, there is little change in T_c, H_irr, and H_c2. Furthermore, charge-carrier mean free path fluctuation, δl pinning, is responsible for the pinning mechanism in Fe_1-xCo_xSe_0.5Te_0.5.

SmBa₂Cu₃O_7-δ (SmBCO) films have been prepared by chemical solution deposition starting from extremely-low-fluorine solutions (7% fluorine with respect to standard full trifluoroacetate solutions). Smooth and homogeneous SmBCO films could be achieved at heating rates of up to 20 °C/min during pyrolysis. The best films were achieved at a crystallization temperature of 810 °C and 50 ppm of oxygen partial pressure. At these conditions, the ~270 nm thick SmBCO films grow mostly c-axis-oriented with $J_{\mathrm{c}}^{\mathrm{sf}}$ values at 77 K of ~2 MA/cm² and critical temperatures T_c of up to 95.0 K. These results demonstrate that using extremely-low-fluorine solutions is very attractive since the production rate can be largely increased due to the solutions’ robustness during pyrolysis retaining a remarkable quality of the grown films. Nevertheless, further optimization of the growth process is needed to improve the superconducting properties of the films.