On the question of metallicity and ferromagnetism in charge ordered insulating Nd0.5Sr0.5MnO3 nanoparticles

TL;DR

This paper investigates how reducing grain size in Nd0.5Sr0.5MnO3 nanoparticles destabilizes charge order, leading to ferromagnetism and metallicity, supported by experiments, theory, and simulations.

Contribution

It offers a universal phenomenological explanation based on surface disorder for size-induced ferromagnetism in charge-ordered manganite nanoparticles.

Findings

Size reduction induces weak ferromagnetism and metallicity.

Surface disorder explains destabilization of charge order.

The mechanism is universal across nanosized charge-ordered manganites.

Abstract

The fascinating phenomenon of destabilization of charge/orbital order in Nd0.5Sr0.5MnO3 with the reduction of grain size is critically investigated. Based on our magnetic and transport experiments followed by a theoretical analysis, we analyze various possible mechanisms and try to delineate a universal scenario behind this phenomenon. We, revisit this issue and discuss the overwhelming evidence from experiments on nano and bulk manganites as well as the absence of correlation between size reduction and pressure effects on manganites. We propose a phenomenological understanding on the basis of enhanced surface disorder to explain the appearance of weak ferromagnetism and metallicity in nanoparticles of Nd0.5Sr0.5MnO3. We also provide supportive evidence from an ab-initio electron structure calculation and a recent numerical simulation and argue that the mechanism is universal in all nanosize charge ordered manganites.