Anomalous spin dynamics in the charge-ordered two-electron doped manganite Ca 0.9 Ce 0.1 Mn O 3 : Possibility of a spin-liquid phase

The 'two-electron' doped rare earth manganites $Ca_1_-_xCe_xMnO_3$ (x = 0.1, 0.2) are probed using resistivity, ac susceptibility and electron paramagnetic resonance (EPR) measurements across their respective charge ordering (CO) temperatures $T_C_O$ = 180 K and 250 K. The EPR 'g' factor and intensity as well as the transport and magnetic behaviors of the two compositions are qualitatively similar and are as expected for CO systems. However, the EPR linewidth, reflective of the spin dynamics, for x = 0.1, shows a strongly anomalous temperature dependence, decreasing with decreasing temperature below $T_C_O$ in contrast with the sample with x = 0.2 and other CO systems. Keeping in view the evidence for magnetic frustration in the system, we propose that the anomalous temperature dependence of the linewidth is the signature of the occurrence of a disorder driven spin liquid phase, present along with charge ordering.