Effect of the Indium Addition on the Superconducting Property and the Impurity Phase in Polycrystalline SmFeAsO1-xFx

We report the increase in the magnetic critical current density (J(c)) of indium added polycrystalline SmFeAsO1-xFx. The value of magnetic J(c) is around 2.5 x 10(4) A/cm(2) at 4.2K under a self-magnetic field. Polycrystalline SmFeAsO1-xFx is mainly composed of superconducting grains and a little amorphous FeAs compounds. These components randomly coexist and amorphous areas are located between superconducting grains. Therefore, superconducting current is prevented from flowing by the amorphous areas. In this study, it is found that indium addition to polycrystalline SmFeAsO1-xFx removes these amorphous areas and induces the clustering of the superconducting grains. This means that the total contact surface area of grains increases. We suggest that the increase in the magnetic J(c) is a direct effect of the indium addition.