Spin dynamics of (Pr 0.5-xCe x)Ca 0.5MnO 3 (x=0.05, 0.10, and 0.20) system studied by muon spin relaxation

Abstract

Muon spin relaxation (μSR) measurements were performed on the (Pr 0.5-xCe x)Ca 0.5MnO 3 (x=0.05, 0.10, and 0.20) manganite system to study the influence of Ce substitution on the spin dynamics. A long-range antiferromagnetic state at low Ce substitution levels (x 0.05) transforms to a spin-glass state by a marginal increase in x to 0.10. The manganite with x=0.05 shows simple exponential relaxation down to low temperatures, whereas the manganites with x=0.10 and 0.20 show a coexistence of two distinct relaxation mechanisms below spin glass-like transition temperature (T G). The μSR data for x=0.10 and 0.20 provide evidence for the existence of a component with a root-exponential relaxation below T G, suggesting a nondiffusive relaxation mechanism similar to that in a magnetic glass. Above T G, the relaxation follows a stretched exponential function with distributed time-scales up to ∼150 K. Although similar types of relaxation dynamics exist in these two manganites (x=0.10 and 0.20), the temperature dependent behavior slightly differ. In the light of the present results, we construct the phase-diagram of the (Pr 0.5-xCe x)Ca 0.5MnO 3 manganite system which encompasses different structural and magnetic correlations evolving as a function of Ce substitution. © 2012 American Institute of Physics.