A nanograined YBCO target, where a great number of grain boundaries, pores etc. exist, is shown to hold an alternative approach to future pulsed laser deposition based high-temperature superconductor thin film and coated conductor technologies. Although the nanograined material is introduced earlier, in this work, we comprehensively demonstrate the modified ablation process, together with unconventional nucleation and growth mechanisms that produces dramatically enhanced flux pinning properties. The results can be generalized to other complex magnetic oxides, where an increased number of defects are needed for modifying their magnetic and electrical properties, thus improving their usability in the future technological challenges.

The effect of in situ oxygen and vacuum annealings on the low bandwidth manganite Gd1−x Ca x MnO3 (GCMO) thin film with x = 0.4 was investigated. Based on the magnetic measurements, the AFM–FM coupling is suppressed by the vacuum annealing treatment via destroying the double exchange interaction and increasing the unit cell volume by converting the Mn4+ to the Mn3+. Consequently, resistance increases significantly compared to pristine film. The results are explained by a model obtained from the positron annihilation studies, where the vacuum annealing increased the annihilation lifetime in A and B sites due to the formation of vacancy complexes V A,B–V O, which was not the case in the pristine sample. The positron annihilation analysis indicated that most of the open volume defects have been detected in the interface region rather than on the subsurface layer and this result is confirmed by detailed x-ray reflection analysis. On the other hand, the effect of oxygen annealing on the unit cell volume and magnetization was insignificant. This is in agreement with positron annihilation results which demonstrated that the introduction of oxygen does not change the number of cation vacancies significantly. This work demonstrates that the modification of oxygen vacancies and vacancy complexes can tune magnetic and electronic structure of the epitaxial thin films to provide new functionalities in future applications.

The effect of in situ annealing is investigated in Gd0.1Ca0.9MnO3 (GCMO) thin films in oxygen and vacuum atmospheres. We show that the reduction of oxygen content in GCMO lattice by vacuum annealing induced more oxygen complex vacancies in both subsurface and interface regions and larger grain domains when compared with the pristine one. Consequently, the double exchange interaction is suppressed and the metallic-ferromagnetic state below Curie temperature turned into spin-glass insulating state. In contrast, the magnetic and resistivity measurements show that the oxygen treatment increases ferromagnetic phase volume, resulting in greater magnetization (MS) and improved magnetoresistivity properties below Curie temperature by improving the double exchange interaction. The threshold field to observe the training effect is decreased in oxygen treated film. In addition, the positron annihilation spectroscopy analysis exhibits fewer open volume defects in the subsurface region for oxygen treated film when compared with the pristine sample. These results unambiguously demonstrate that the oxygen treated film with significant spin memory and greater magnetoresistance can be a potential candidate for the future memristor applications.