EPR studies on single crystals of Pr1-xPbxMnO3Pr1-xPbxMnO3

Electron paramagnetic resonance (EPR) studies are carried out on single crystals of Pr1-xPbxMnO3Pr1-xPbxMnO3, for x=0.23x=0.23 and 0.30. The crystal with x=0.23x=0.23 undergoes a transition from paramagnetic insulator to ferromagnetic insulator with Curie temperature TC∼167K. The crystal with x=0.30x=0.30 undergoes a transition from paramagnetic insulator to ferromagnetic metal with TC∼200K. The EPR analysis is carried out in the paramagnetic region for both the crystals. The EPR signals are fitted to the Dysonian equation. Linewidth, intensity and asymmetry parameters are plotted as a function of temperature down to TCTC. The intensity shows a simple Curie–Weiss behaviour. The spin relaxation takes place through a “bottleneck” mechanism according to which linewidth depends only on strong exchange interaction between Mn3+Mn3+ and Mn4+Mn4+ ions. Around 240 K a secondary low field EPR signal is observed for both compositions which persists till around 200 K indicating a possible phase separation.