  Some new members of a Ruthenocuprate (2212) series have been synthesized by
Mn substitution for Ru in Gd1.4Ce0.6Sr2RuCu2O10 . Characterisation by XRD phase
analysis followed by Rietveld refinement has been carried out. IR spectroscopy
studies and Rietveld refinements are consistent with substitution of Mn at Ru
site. XRD studies indicate changes in structural features on substitution
including a significant change in lattice parameter for a very low substitution
level (1mole% of Ru). The pristine compound shows coexistence of
superconductivity and magnetism. Four probe resistivity studies indicate a
semiconductor like upturn in resistivity and absence of superconductivity even
for Mn substitution levels as low as 1 mole%. a. c. susceptibility measurements
show a progressive suppression of the magnetic transition temperature as well
as a smearing of the magnetic transition as a function of Mn substitution.
Possible reasons for absence of superconductivity have been discussed.
