Effect of Nanorod Alignment on Flux Pinning State in BaHfO3 Doped SmBa2Cu3 Oy Films

The effect of the microstructure on the flux pinning state in BaHfO₃(BHO) nanorods doped SmBa₂ Cu₃O_y(SmBCO) films was investigated using high field magnets with a rotator stage. Films with aligned nanorods showed the strong flux pining along c-axis, which disappears at high magnetic fields. This behavior corresponds to the existence of the Bose glass state in the film, which is also supported by the behaviors of the activation energy and the critical exponent of the liquid-glass transition estimated from the transport properties. Moreover, the field dependencies of the flux pinning force are explained by the flux pinning models for the correlated nanorods and the random pinning centers in the films with the aligned and the firework nanorods structures. The strong relationship is confirmed between the structure of the nanorods and the pinning properties in the BHO doped SmBCO films.