Anisotropy of flux pinning properties in superconducting (Li,Fe)OHFeSe thin films

The electrical transport properties of (Li,Fe)OHFeSe films have been investigated in detail. The sharply textured films, prepared by matrix-assisted hydrothermal epitaxy (MHE) on LaAlO3, show a zero-resistance critical temperature Tc of ∼42 K, Jc values well above 1 MA cm−2 at low temperatures, and a maximum pinning force density FP of ∼100 GN m−3 at 4 K. The activation energy U0 for thermal depinning of flux lines has been resolved for low magnetic fields, it agrees well with literature data. The coherence lengths and penetration depth were estimated via upper critical field Bc2 and self-field Jc, respectively, to be ξab ∼ 2.7 nm, ξc = 0.24 nm, and λab ∼ 160-200 nm. The layered crystal structure leads to highly anisotropic and two-dimensional electrical properties, including trapping and lock-in of vortices.