Effect of oxygen isotope substitution and crystal micro-structure on magnetic ordering and phase separation in {$\rm (La_{1-y}Pr_{y})_{0.7}Ca_{0.3}MnO_3$}

TL;DR

This study investigates how oxygen isotope substitution and crystal microstructure influence magnetic ordering and phase separation in a manganite system, revealing the roles of polaronic effects and quenched disorder near the metal-insulator transition.

Contribution

It provides a quantitative analysis of how lattice micro-strains and isotope effects affect phase separation and magnetic properties in manganites.

Findings

Polaronic narrowing impacts carrier bandwidth and phase fractions.

Quenched disorder influences the suppression of long-range order.

Transition temperatures exhibit a dip near the metal-insulator transition.

Abstract

The crystal and magnetic structures of the specified CMR manganite system have been studied as a function of $y=(0.2-1)$ across the metal-insulator (MI) transition, and of the oxygen mass ($^{16}$O, $^{18}$O). We quantitatively show how the polaronic narrowing of the carrier bandwidth and the crystal lattice micro-strains control the volume fractions of the mesoscopic ferro- and antiferromagnetic clusters. A well-defined dip in the transition temperatures and the suppression of all the types of long range ordering seen near the MI-transition at $y\simeq0.9$ indicate a key role of the quenched disorder for the formation of the long-scale phase separated state.