Vortex structure and magnetic properties of BaFe2(As1−xPx)2 single crystals

Abstract

Magnetic decoration of BaFe2(As1−xPx)2 revealed an hexagonal vortex lattice in overdoped single crystals (x>0.4, Tc=14-18 K). A disordered vortex lattice was observed in a crystals with optimal content of phosphorus (x ≈ 0.4, Tc = 25-30 K). Magneto-optical studies and global magnetization measurement of the optimally-doped crystal have led to an estimated critical current density of ~ 105A/cm2 at 5-12 K in fields up to 0.7 T. This high critical current density suggests strong pinning, probably due to defects, a result consistent with the observed disordered vortex lattice. The critical current density of the overdoped crystal is much smaller, i.e. ~ 104 A/cm2 at 5 K in fields up to 0.1 T, decreasing to virtually zero at 0.3 T.