Revealing polarons with high pressure on low electron-doped manganites

TL;DR

This study investigates how applying high pressure affects the electrical and magnetic properties of low electron-doped manganites, revealing insights into polaron behavior and electron-phonon interactions.

Contribution

It provides experimental evidence of pressure effects on low electron-doped manganites and interprets results within a modified Double Exchange model involving Fröhlich polarons.

Findings

Weak pressure dependence of Curie temperature (~6 K GPa$^{-1}$)

Pressure influences electron bandwidth via electron-phonon interactions

Results support a polaron-based interpretation of electronic behavior

Abstract

Pressure sensitivity (up to 1 GPa) of the electrical resistivity and of the ac susceptibility was measured for low electron doping levels of Ca$_{1-x}$Y$_x$MnO$_3$ (CYMO) and of Ca$_{1-x}$Sm$_x$MnO$_3$ (CSMO) ceramic samples (0.05 $\leq$ x $\leq$ 0.15). A very weak pressure dependence of the Curie temperature (T$_c$) was observed for both systems ($\sim$ 6 K GPa$^{-1}$), when compared to the hole-doped manganites of the same T$_c$ ($\sim$ 20 K GPa$^{-1}$). Our results can be interpreted within a modified Double Exchange scenario, where pressure alters the reduction of the bandwidth produced by the electron-phonon interaction associated with small Fr\"{o}hlich polarons in the weak to intermediate coupling regime.