Magnetization and ESR studies of La0.67(Ca1−xMgx)0.33MnO3 systems

Magnetization studies and line shape analysis on Electron Spin Resonance (ESR) spectra of La0.67(Ca1−xMgx)0.33MnO3 are carried out. In paramagnetic phase well above Tc, the ESR spectra are single Lorentzian but below and near T∗ΔHPP, (T∗ΔHPP is temperature at which line width is minimum) inhomogeneous broadening with asymmetry in the signal is observed due to phase separation. The resonance field below T∗ΔHPP decreases with decreasing temperature. Above Tc the intensity of the ESR spectra obeys the thermally activated model (Arrhenius behavior). Substitution of Mg weakens the ferromagnetic interaction and evolution of change in lineshape near Tc is an evidence of Griffiths phase (coexistence of paramagnetic and ferromagnetic) in Mg doped LCMO system.