Spin dynamics of (Pr0.5-xCex)Ca0.5MnO3 (x = 0.05, 0.10, and 0.20) system studied by muon spin relaxation

Abstract

Muon spin relaxation (μSR) measurements were performed on the (Pr0.5-xCex)Ca0.5MnO3 (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 (TG). The μSR data for x = 0.10 and 0.20 provide evidence for the existence of a component with a root-exponential relaxation below TG, suggesting a nondiffusive relaxation mechanism similar to that in a magnetic glass. Above TG, 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 (Pr0.5-xCex)Ca0.5MnO3 manganite system which encompasses different structural and magnetic correlations evolving as a function of Ce substitution.