Anomalous paramagnetic behavior in the paramagnetic phase of La2/3−xYxCa1/3MnO3 studied through EPR and its relation to colossal magnetoresistance

Electron paramagnetic resonance on La2/3−xYxCa1/3MnO3 in the paramagnetic (PM) regime TC<T<450 K is presented for 0≤x≤0.133. The resonance linewidth (ΔHpp) decreases with cooling, reaches the minimum at Tmin, and then anomalously increases with further cooling toward Tc. Our analysis on ΔHpp(T) below Tmin shows that the anomalous PM behavior below Tmin is due to the appearance of a ferromagnetic (FM) phase within the PM matrix caused by the applied magnetic fields. The correlation between the anomalous PM and the colossal magnetoresistance is discussed. We argue that both are caused by the phase segregation in which the compound is phase-separated into a mixture of FM and PM regions.