Improvement of Flux Pinning Properties for Hafnium-Doped Gd123 Thin Films Fabricated by a Fluorine-Free MOD Method

Abstract

In order to enhance the flux pinning force density $F_{p}$ in magnetic fields for REBa2Cu3O $_{y}$ (RE123)-coated conductors, Hf and Zr doping are the very valid way of introducing the perovskite nanostructure as artificial pinning centers (APCs) into the superconductors. However, the studies for Hf-doped RE123 thin films fabricated by the fluorine-free metal organic deposition (FF-MOD), which is the easiest production process, have not been done yet. In this study, we have successfully fabricated Hf-doped FF-MOD GdBa2 Cu3O $_{y}$ (Gd123) thin films on LaAlO3 substrates and investigated their flux pinning properties. Critical temperature for Gd123 thin films indicated around 92 K, and $T_{c}$ varied little by Hf doping. Hf 10 mol% doped film achieved high critical current densities of 2.72 mA⋅cm −2 at 77.3 K under 0 T, and 0.27 mA⋅cm−2 at 77.3 K under 1 T. With increasing Hf-doping amount, $F_{p}$ gradually increased, and the peak of $F_{p}$ shifted to the high magnetic field side. The elementary pinning force and the effective pinning center density also increased. We believe that effective APCs, probably BaHfO3 are introduced into FF-MOD Gd123 thin films by Hf doping.