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 TC up to 55 K. Doping with the smaller Gd3+ results in lattice contraction and thereby
enhances TC. It is interesting to observe that though Ce3+ doping in SmFeAsO0.7F0.3 exhibits an increase
in lattice parameters, a substantial enhancement of TC occurs. The enhancement in TC due to increased
charge carrier concentration is also confirmed using Hall Effect measurement. Apart from TC enhancement,
the simultaneous doping of both at oxygen and rare earth sites prominently increases the superconducting
properties such as JC, HC1 and HC2. The co-doped samples also exhibit better magnetic field
dependence of JC over the entire field of study. It is also observed that the Ce3+ doped sample shows
higher JC in the high field region due to its enhanced flux pinning properties.
