Evolution of the low-frequency spin dynamics in ferromagnetic manganites

TL;DR

This study investigates the evolution of low-frequency spin dynamics in ferromagnetic manganites using neutron scattering, revealing distinct behaviors near the Curie temperature and clarifying previous inconsistencies in the field.

Contribution

It provides new insights into the temperature-dependent spin dynamics of manganites, highlighting the formation of spin clusters near $T_c$ in one compound and a conventional transition in another.

Findings

Spin clusters of ~20 Å form near $T_c$ in the 197.9 K sample.

The 300.9 K sample exhibits a more conventional paramagnetic to ferromagnetic transition.

Results clarify systematics in the spin dynamics of manganites.

Abstract

Elastic and inelastic neutron scattering was used to study two ferromagnetic manganites A$_{1-x}$B$_{x}$MnO$_3$ (x $\approx$ 0.3) with $T_c$=197.9 K and 300.9 K. The spin dynamical behavior of these is similar at low temperatures, but drastically different at temperatures around $T_c$. While the formation of spin clusters of size ($\sim20$ \AA) dominates the spin dynamics of the 197.9 K sample close to $T_c$, the paramagnetic to ferromagnetic transition for the 300.9 K sample is more conventional. These results, combined with seemingly inconsistent earlier reports, reveal clear systematics in the spin dynamics of the manganites.