  We report on resistivity measurements in La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ and
Nd$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films in order to elucidate the underlying
mechanism for the CMR behavior. The experimental results are analyzed in terms
of quantum phase transition ideas to study the nature of the metal-insulator
transition in manganese oxides. Resistivity curves as functions of
magnetization for various temperatures show the absence of scaling behavior
expected in a continuous quantum phase transition, which leads us to conclude
that the observed metal-insulator transition is most likely a finite
temperature crossover phenomenon.
