  For the first time,we report the effect of pentavalent subtitution at the Mn
site of La(0.67)Ca(0.33)MnO(3). The ferromagnetic -metallic ground state
modifies to a cluster-glass insulator beyond x=0.03. The observed suppression
in the transition temperatures (39K/at.%) is the largest reported for the Mn
site subtituted manganites. We argue that charge state(valence) of the
substituent has a dominant role in affecting the ferromagnetic - metallic
ground state of CMR manganites.
