The essential role of magnetic frustration in the phase diagrams of doped cobaltites

TL;DR

This paper demonstrates that magnetic frustration is crucial in understanding the phase diagrams of doped cobaltites, explaining the delayed onset of long-range ferromagnetism through Monte-Carlo simulations.

Contribution

It reveals the essential role of magnetic frustration in the phase behavior of doped cobaltites, resolving previous inconsistencies in their magnetic phase diagrams.

Findings

Magnetic frustration delays long-range ferromagnetism onset.

Monte-Carlo simulations accurately reproduce experimental phase diagrams.

Magnetic frustration explains the discrepancy between polaron percolation and ferromagnetism onset.

Abstract

Doped perovskite cobaltites (e.g., La$_{1-x}$Sr$_x$CoO$_3$) have been extensively studied for their spin-state physics, electronic inhomogeneity, and insulator-metal transitions. Ferromagnetically-interacting spin-state polarons emerge at low $x$ in the phase diagram of these compounds, eventually yielding long-range ferromagnetism. The onset of long-range ferromagnetism ($x \approx 0.18$) is substantially delayed relative to polaron percolation ($x \approx 0.05$), however, generating a troubling inconsistency. Here, Monte-Carlo simulations of a disordered classical spin model are used to establish that previously ignored magnetic frustration is responsible for this effect, enabling faithful reproduction of the magnetic phase diagram.