Influence of rare earth doping on the structural and electro-magnetic properties of SmFeAsO0.7F0.3 iron pnictide

Abstract

The effects of rare earth site doping on the structural, superconducting and magnetic properties of SmFeAsO0.7F0.3 iron pnictide are investigated. Gd3+ and Ce3+ ions are chosen by virtue of their position being on either side of Sm3+. Doping of both smaller (Gd3+) and larger (Ce3+) ions at the Sm3+ site increases the T-C up to 55 K. Doping with the smaller Gd3+ results in lattice contraction and thereby enhances T-C. It is interesting to observe that though Ce3+ doping in SmFeAsO0.7F0.3 exhibits an increase in lattice parameters, a substantial enhancement of T-C occurs. The enhancement in T-C due to increased charge carrier concentration is also confirmed using Hall Effect measurement. Apart from T-C enhancement, the simultaneous doping of both at oxygen and rare earth sites prominently increases the superconducting properties such as J(C), H-C1 and H-C2. The co-doped samples also exhibit better magnetic field dependence of J(C) over the entire field of study. It is also observed that the Ce3+ doped sample shows higher J(C) in the high field region due to its enhanced flux pinning properties.