Internal friction evidence of the intrinsic inhomogeneity in La0.67Ca0.33MnO3 at low temperatures

The ferromagnetic manganite La0.67Ca0.33MnO3 is systematically investigated below Curie temperature T-C by measurements of internal friction Q(-1)(T), Young's modulus E(T), resistivity rho(T), and magnetization M(T). Accompanying single metal-insulator transition at T-p and single paramagnetic-ferromagnetic (PM-FM) transition, three peaks at temperatures 260, 222, and 105 K are observed in the spectra of internal friction Q(-1)(T), respectively. The two peaks at 260 and 105 K are of the characteristic of the phase transition, which are related to the magnetic transition from a PM disorder state to a FM order state and to the intrinsic inhomogeneity due to the electronic phase separation, respectively. The broad peak around 222 K is actually composed of two subpeaks located at 222 and 234 K, respectively. This broad peak is of the characteristic of relaxation originating from the thermally activated motion of insulating and conduction domains. The activation energy and the relaxation time at infinite temperature are determined as 0.32 eV, 2.0x10(-12) s for the 222-K subpeak and 0.38 eV, 2.5x10(-13) s for the 234-K subpeak, respectively.