Structure, Tranport and Magnetism of La(0.67)Ca(0.33)Mn(1-x)Ta(x)O(3)
  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. 
L.Seetha Lakshmi, K.Doerr, K. Nenkov, V.Sridharan, V.S.Sastry and   K.-H.Mueller