Magneto-optical characterizations of FeTe_0.5Se_0.5 thin films with critical current density over 1 MA cm⁻²

We performed magneto-optical (MO) measurements on FeTe_0.5Se_0.5 thin films grown on LaAlO₃ (LAO) and Yttria-stabilized zirconia (YSZ) single-crystalline substrates. These thin films show superconducting transition temperature T_c ∼19 K, 4 K higher than the bulk sample. Typical roof-top patterns can be observed in the MO images of thin films grown on LAO and YSZ, from which a large and homogeneous critical current density J_c over 1×10⁶ A cm⁻² at 5 K was obtained. Magnetic flux penetration measurement reveals that the current is almost isotropically distributed in the two thin films. Compared with bulk crystals, FeTe_0.5Se_0.5 thin film demonstrates not only higher T_c, but also much larger J_c, which is attractive for applications. (paper)