Abstract: The internal frictions and elastic moduli of colossal magnetoresistance material La_0.7Pb_0.3MnO₃ were measured on multi-function internal friction apparatus with the low frequency torsion pendulum.
The inverse proportionality of the peak height against the measurement frequency and the invariance of the peak position by changing frequencies are typical features of phase transition. The corresponding
elastic modulus with a local minimum at internal friction peaks also characterizes the nature of phase transition. The relationships between double peaks of internal friction and the double peaks of electric resistance
versus temperature were explaned by studying the colossal magnetoresistance effect and the susceptibility. The internal friction peak and resistance peak at higher temperatures correspond well with Curie temperature,
ascribed to a transition from PMI to FMM. The internal friction peak at lower temperatures and the monotony descending of susceptibility may be interpreted as the phase separation originated from an inhomogeneous
distributing of electric and magnetic phase, whereas the high resistance peak at lower temperatures may be partly from the phase separation.

Key words: colossal magnetoresistance effect （CMR）, internal friction, phase separation