Evidence for strong effect of quenched correlated disorder on phase separation and magnetism in (La_{1-y}Pr_{y})_{0.7}Ca_{0.3}MnO_3

TL;DR

This study demonstrates that quenched correlated disorder significantly influences phase separation and magnetic properties in (La_{1-y}Pr_{y})_{0.7}Ca_{0.3}MnO_3, with disorder strength affecting phase composition and transition temperatures.

Contribution

It provides direct evidence that correlated quenched disorder controls phase separation and magnetic transitions in this manganite system, highlighting the role of synthesis procedures and micro-strain.

Findings

Correlated disorder affects phase separation and T_C.

Ground state is FM-like with ~20% AFM phase.

Oxygen isotope substitution transforms magnetic states.

Abstract

High resolution neutron diffraction shows that the mesoscopic separation into ferromagnetic (FM) and antiferromagnetic (AFM) phases and the FM transition temperature T_C in the perovskite manganite (La_{1-y}Pr_{y})_{0.7}Ca_{0.3}MnO_3 strongly depend on the quenched correlated disorder. The different disorder strengths are achieved by different procedures of the sample synthesis and quantitatively characterized by the micro-strain-type diffraction peak broadening. The system shifts to predominantly one phase state with smaller T_C as the correlated disorder strength is decreased supporting the viewpoint that the origin of phase separation in the indicated manganite system is the correlated quenched disorder. The ground state of an ultimately chemically homogeneous sample is FM-like containing about 20% of the AFM minority phase. This FM-like state can be readily transformed to the AFM-like one having <20% of FM-phase by the decreasing of the effective charge carrier bandwidth via oxygen isotope substitution.