Electron Paramagnetic Resonance Study of Phase Segregation in Nd₀.₅Sr₀.₅MnO₃

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We present results of an electron paramagnetic resonance (EPR) study of Nd₁₋ₓSrₓMnO₃ with x = 0.5 across the paramagnetic to ferromagnetic, insulator to metal transition at 260 K (Tc) and the antiferromagnetic, charge ordering transition (Tₙ = Tco) at 150 K. The results are compared with those on Nd₀.₄₅Sr₀.₅₅MnO₃ which undergoes a transition to a homogeneous A-type antiferromagnetic phase at Tₙ = 230 K and on La₀.₇₇Ca₀.₂₃MnO₃ which undergoes a transition to coexisting ferromagnetic metallic and ferromagnetic insulating phases. For x = 0.5, the EPR signals below Tc consist of two Lorentzian components attributable to the coexistence of two phases. From the analysis of the temperature dependence of the resonant fields and intensities, we conclude that in the mixed phase ferromagnetic and A-type antiferromagnetic (AFM) phases coexist. The x = 0.55 compound shows a single Lorentzian throughout the temperature range. The signal persists for a few degrees below Tₙ. The behaviour of the A-type AFM phase is contrasted with that of the two ferromagnetic phases present in La₀.₇₇Ca₀.₂₃MnO₃. The comparison of behaviour of A-type AFM signal observed in both Nd₀.₅Sr₀.₅MnO₃and Nd₀.₄₅Sr₀.₅₅MnO₃with the two FM phases of La₀.₇₇Ca₀.₂₃MnO₃, vis-a-vis the shift of resonances with respect to the paramagnetic phases and the behaviour of EPR intensity as a function of temperature conclusively prove that the Nd₀.₅Sr₀.₅MnO₃undergoes phase separation into A-type AFM and FM phases.