Phase Competition in Ln0.5a0.5mno3 Perovskites

TL;DR

This study investigates phase competition in Ln0.5A0.5MnO3 perovskites, revealing a critical tolerance factor where a unique ferromagnetic phase emerges, separating charge-ordered and itinerant electronic behaviors, with insights from pressure experiments.

Contribution

It identifies a critical tolerance factor in Ln0.5A0.5MnO3 perovskites where a distinct ferromagnetic phase appears, advancing understanding of phase transitions in these materials.

Findings

Ferromagnetic phase appears at critical tolerance factor tc=0.975.

Distinct charge-ordered and itinerant phases are separated by this ferromagnetic phase.

Pressure experiments reveal effects of chemical vs. hydrostatic pressure on phase competition.

Abstract

Single crystals of the systems Pr0.5(Ca1-xSrx)0.5MnO3, (Pr1-yYy)0.5(Ca1-xSrx)0.5MnO3, and Sm0.5Sr0.5MnO3 were grown to provide a series of samples with fixed ratio Mn(III)/Mn(IV)=1 having geometric tolerance factors that span the transition from localized to itinerant electronic behavior of the MnO3 array. A unique ferromagnetic phase appears at the critical tolerance factor tc= 0.975 that separates charge ordering and localized-electron behavior for t<tc from itinerant or molecular-orbital behavior for t>tc. This ferromagnetic phase, which has to be distinguished from the ferromagnetic metallic phase stabilized at tolerance factors t>tc, separates two distinguishable Type-CE antiferromagnetic phases that are metamagnetic. Measurements of the transport properties under hydrostatic pressure were carried out on a compositions t a little below tc in order to compare the effects of chemical vs. hydrostatic pressure on the phases that compete with one another near t=tc.