Effect of carrier doping on the formation and collapse of magnetic polarons in lightly hole-doped La_{1-x}Sr_xCoO_3

TL;DR

This study explores how carrier doping influences the formation and collapse of magnetic polarons in lightly hole-doped La_{1-x}Sr_xCoO_3, revealing two regimes of phase separation and the transition from polarons to magnetic clusters.

Contribution

It provides new insights into the doping-dependent magnetic inhomogeneities and phase separation mechanisms in cobalt perovskites, supported by neutron scattering and magnetization data.

Findings

Magneto-electronic phase separation occurs in lightly doped La_{1-x}Sr_xCoO_3.

Higher doping leads to decay of spin-state polarons and formation of magnetic clusters.

Two regimes of phase separation are identified based on doping levels.

Abstract

We investigate the doping dependence of the nanoscale electronic and magnetic inhomogeneities in the hole-doping range 0.002<x<0.1 of cobalt based perovskites, La{1-x}Sr_xCoO_3. Using single crystal inelastic neutron scattering and magnetization measurements we show that the lightly doped system exhibits magneto-electronic phase separation in form of spin-state polarons. Higher hole doping leads to a decay of spin-state polarons in favor of larger-scale magnetic clusters, due to competing ferromagnetic correlations of Co^{3+} ions which are formed by neighboring polarons. The present data give evidence for two regimes of magneto-electronic phase separation in this system: (i) x<0.05, dominated by ferromagnetic intrapolaron interactions, and (ii) x>0.05, dominated by Co^{3+}-Co^{3+} intracluster interactions. Our conclusions are in good agreement with a recently proposed model of the phase separation in cobalt perovskites [He et al., Europhys. Lett. 87, 27006 (2009)].