Improved superconducting properties of skutterudite La3Co4Sn13 with indium substitution
We report on two fold increase in superconducting transition temperature of La3Co4Sn13 by substituting indium at the tin site. The transition temperature of this skutterudite is observed to increase from 2.5 K to 5.1 K for 10 % indium substituted sample. The band structure and density of states calculations also indicate such a possibility. The compounds exhibit type - II superconductivity and the values of lower critical field (Hc1), upper critical field (Hc2), Ginzburg - Landau coherence length , penetration depth and GL parameter are estimated to be 0.0028 T, 0.68 T, 21.6 nm, 33.2 nm and 1.53 respectively for La3 Co4Sn11.7In1.3. Hydrostatic external pressure leads to decrease in transition temperature and the calculated pressure coefficient is -0.311 K/GPa . Flux pinning and vortex activation energies also improved with indium addition. Only positive frequencies are observed in phonon dispersion curve that relate to the absence of charge density wave or structural instability in the normal state.