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

Abstract

Doped perovskite cobaltites (e.g., La1􀀀xSrxCoO3) have been extensively studied for their spin-state physics, electronic inhomogeneity, and insulator-metal transitions. Ferromagneticallyinteracting 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 ≈ 0.18) is substantially delayed relative to polaron percolation (x ≈ 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 e ect, enabling faithful reproduction of the magnetic phase diagram.