Magnetic granularity in pulsed laser deposited YBCO films on technical templates at 5 K

Abstract

The manifestation of granularity in the superconducting properties of pulsed laser depositedYBCOfilms on commercially available metallic templates was investigated by scanning Hallprobe microscopy at 5 K and was related to local orientation mapping of the YBCO layer. TheYBCOfilms on stainless steel templates with a textured buffer layer of yttrium stabilized ZrO2grown by alternating beam assisted deposition have a mean grain size of less than1mmwith asharp texture. This results in a homogeneous trappedfield profile and spatial distribution of thecurrent density. On the other hand, YBCOfilms on biaxially textured NiW substrates showmagnetic granularity that persists down to a temperature of 5 K and up to an applied magneticfield of 4 T. The origin of the granularfield profile is directly correlated to the microstructuralproperties of the YBCO layer adopted from the granular NiW substrate which leads to a spatiallyinhomogeneous current density. Grain-to-grain in-plane tilts lead to grain boundaries thatobstruct the current while out-of-plane tilts mainly affect the grain properties, resulting in areaswith lowJc. Hence, not all grain boundaries cause detrimental effects onJcsince the orientationof individual NiW grains also contributes to observed inhomogeneity and granularity