Two-Phase Paramagnetic-Ferromagnetic State of La_(0.7)Pb_(0.3)MnO_3 Single-Crystal Lanthanum Manganite

摘要

Two phases, paramagnetic and ferromagnetic, were shown by the magnetic resonance method to coexist below the temperature T_c in La_(0.7)Pb_(0.3)MnO_3 single crystals exhibiting colossal magnetoresistance. The magnetic resonance spectra were studied in the frequency range 10-78 GHz. The specific features in the behavior of the spectral parameters were observed to be the strongest at the temperatures corresponding to the maximum magnetoresistance in the crystals. The concentration ratios of the paramagnetic and ferromagnetic phases in the samples were found to be sensitive to variations in temperature and external magnetic field. This behavior suggests realization of the electronic phase separation mechanism in the system under study.