Formation and pinning properties of growth-controlled nanoscale precipitates inYBa2Cu3O7−δ/transition metal quasi-multilayers

Abstract

To study the possibility of enhancing the pinning forces inYBa2Cu3O7−δ films through the introduction of nanosized precipitates, quasi-multilayers ofYBa2Cu3O7−δ and a transition metal(TM = Ti,Zr,Hf) were depositedon single-crystal SrTiO3 substrates using pulsed laser deposition. The transition metal layer thickness was chosen to be less thanone unit cell, resulting in separated nanoscale islands that form inclusions with perovskite structureBaTM O3 during film growth. These inclusions grow biaxially textured within the film.Whereas the Ti-doped films show a very strong decrease in the critical temperatureTc and, hence, a strong decrease in the critical current densityJc with increasing TM amount for all temperatures, Hf and Zr doping show an increase inJc for the smallest amounts of doping. An irreversibility field as high as 10.3 T at 77 K wasobserved in the case of low Hf content.