Huge critical current density and tailored superconducting anisotropy in SmFeAsO0.8F0.15 by low-density columnar-defect incorporation

Iron-based superconductors could be useful for electricity distribution and superconducting magnet applications because of their relatively high critical current densities and upper critical fields. SmFeAsO 0.8 F 0.15 is of particular interest as it has the highest transition temperature among these materials. Here we show that by introducing a low density of correlated nano-scale defects into this material by heavy-ion irradiation, we can increase its critical current density to up to 2 × 10 7 A cm −2 at 5 K—the highest ever reported for an iron-based superconductor—without reducing its critical temperature of 50 K. We also observe a notable reduction in the thermodynamic superconducting anisotropy, from 8 to 4 upon irradiation. We develop a model based on anisotropic electron scattering that predicts that the superconducting anisotropy can be tailored via correlated defects in semimetallic, fully gapped type II superconductors. Iron-based superconductors could be useful in the development of superconducting magnets and related applications. Fang et al . show that a low density of columnar defects in SmFeAsO 0.8 F 0.15 can increase its critical current to record-high values and reduce its superconducting anisotropy.