Softening and Broadening of the Zone Boundary Magnons in Pr0.63Sr0.37MnO3

TL;DR

This study investigates the spin dynamics in Pr$_{0.63}$Sr$_{0.37}$MnO$_3$, revealing temperature-dependent magnon behavior that challenges existing models and suggests evolving magnetic interactions near the Curie temperature.

Contribution

It provides new insights into the spin excitations and their temperature dependence in a specific manganite compound, highlighting deviations from traditional double exchange models.

Findings

Magnon dispersion softens at the zone boundary below T_C

Zone boundary magnons broaden significantly as T approaches T_C

No residual spin-wave excitations observed above T_C

Abstract

We have studied the spin dynamics in Pr$_{0.63}$Sr$_{0.37}$MnO$_3$ above and below the Curie temperature $T_C=301$ K. Three distinct new features have been observed: a softening of the magnon dispersion at the zone boundary for $T<T_C$, significant broadening of the zone boundary magnons as $T\to T_C$, and no evidence for residual spin-wave like excitations just above $T_C$. The results are inconsistent with double exchange models that have been successfully applied to higher $T_C$ samples, indicating an evolution of the spin system with decreasing $T_C$.