Double metal-insulator transitions and magnetoresistance:An intrinsic   feature of Ru substituted La(0.67)Ca(0.33)MnO(3)
  In this paper, we examine the possible influence of extrinsic factors on the electrical and magnetotransport of La(0.67)Ca(0.33)Mn(1-x)Ru(x)O(3) (x < 0.10). These results not only exclude the extrinsic factors, but establishes the fact that the metal transitions both exhibiting MR is intrinsic to Ru substituted La(0.67)Ca(0.33)MnO(3) and the system. These results substantiate our hypothesis that Ru substituted system undergoes a magnetic phase separation involving the co-existence of two ferromagnetic-metallic phases in its ground state. 
L. Seetha Lakshmi, V. Sridharan, R. Rawat, A. A. Sukumar, M. Kamuddin,   V. S. Sastry, V. S. Raju