  The effect of doping Mo for Mn on the magnetic and transport properties of
the colossal magnetoresistance material, La0.67Ba0.33MnO3, has been studied.
Compounds of the series La0.67Ba0.33Mn1-xMoxO3 (x=0.0 to 0.1) have been
prepared and found to crystallize in the orthorhombic structure (space group
Pbnm). Energy Dispersive X-ray Analysis (EDAX) measurements confirm the
stoichiometry of all the samples. Magnetotransport and magnetization
measurements reveal that the metal-insulator transition temperature (Tp)
decreases from 330K for x=0 to 255K for x=0.1. The change in Tp on Mo
substitution is relatively much smaller than the corresponding change observed
on substitution by other transition elements, such as Ti, Fe, Co, Ni, etc.
Further, the ferromagnetic transition temperature (TC) is nearly unchanged by
Mo substitution. This is in striking contrast to the large decrease in TC
observed with substitution of above-mentioned 3d elements. These unusual
magnetic and transport properties of La0.67Ba0.33Mn1-xMoxO3 may be either due
to the formation of magnetic pair between Mn and Mo or due to strong
Mo(4d)-O(2p) overlap, which in turn, may affect the Mn-Mn interaction via the
oxygen atoms
