An electron paramagnetic resonance study of phase segregation in Nd0.5Sr0.5MnO3

We present results of an electron paramagnetic resonance (EPR) study of Nd1−x Sr x MnO3 with x=0.5 across the paramagnetic to ferromagnetic, insulator to metal transition at 260K (T c) and the antiferromagnetic, charge ordering transition (T N=T co) at 150K. The results are compared with those on Nd0.45Sr0.55MnO3 which undergoes a transition to a homogeneous A-type antiferromagnetic phase at T N=230K 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 T c 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 T N. 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 Nd0.5Sr0.5MnO3 and Nd0.45Sr0.55MnO3 with the two FM phases of La0.77Ca0.23MnO3, vis-à-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 Nd0.5Sr0.5MnO3 undergoes phase separation into A-type AFM and FM phases.