GdBa₂Cu₃O_7-d (GdBCO) thin films with artificial pinning centers (APCs) have been investigated for practical applications due to their large critical current density (J_c) over wide range of temperature and applied magnetic field [1]. Some of the APCs tend to self-assemble as nanorods inside the superconducting GdBCO film matrix. These APCs include Ba based perovskite materials such as BaZrO₃, BaHfO₃, BaSnO₃. The diameter of the nanorods of these Ba based perovskite materials have been reported to be in the range of ~ 6-10 nm which is substantially higher than the coherence length (ξ_ab) of GdBCO superconductor at lower temperatures and that is why thinner nanorods are desired to be incorporated inside GdBCO film matrix. The large concentration of thinner nanorods are expected to increase the matching field with minimal loss of superconducting volume fraction and enhance the vortex pinning properties of GdBCO thin films even at lower temperatures.

There has been considerable interest in incorporating thinner nanorods inside GdBCO films by different techniques which include selection of suitable APC materials, variation in the depositions conditions etc. It has been predicted that some materials such as (Sr/Ca)HfO₃ would form nanorods with much smaller diameter compared to their Ba based counterparts due to the decay of the strain generated at the interface of superconducting GdBCO and insulating APCs [2]. We have studied the incorporation of CaHfO₃ nanoinclusions inside GdBCO superconducting film matrix and subsequently the vortex pinning properties of the nanocomposite films. In this paper, the structural, microstructural and transport properties of GdBCO thin films incorporating varying concentrations of CaHfO₃ will be discussed. The concentration of CaHfO₃ nanoinclusions can be controlled in PLD system using surface modified target approach.

Reference:
[1] Alok K. Jha and Kaname Matsumoto, Front. Phys. 7, 82 (2019). 
[2] J. Wu and J. Shi, Supercond. Sci. Technol. 30, 103002 (2017).