Regensburg 2019 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 54: Correlated Electrons: Complex Oxides and Other Materials

TT 54.3: Vortrag

Donnerstag, 4. April 2019, 10:00–10:15, H22

Percolation of frustrated polarons in the doped perovskite cobaltite La_1−xSr_xCoO_3−δ — •Peter P. Orth¹, Daniel Phelan², Chris Leighton³, and Rafael Fernandes³ — ¹Iowa State University, USA — ²Argonne National Laboratory, USA — ³University of Minnesota, USA

Due to fascinating phenomena such as magneto-electronic phase separation and Co ion spin-state transitions, the archetypal cobaltite La_1−xSr_xCoO_3−δ (LSCO) remains of high interest. Chemical substitution of La by Sr introduces both holes and magnetic moments into the diamagnetic parent compound. The tendency of Co to undergo spin-state transitions leads to the formation of 7-site spin polarons. Further doping results in a glassy magnetic state that transforms at x=0.18 into a ferromagnetic metal. As simple statistical considerations predict a percolation of polarons at much smaller values of x=0.05, this raises the question what suppresses the formation of ferromagnetism. Here, we address this question within a microscopic model capturing both competing magnetic interactions between the Co moments in different spin states as well the spatial inhomogeneity introduced by disorder. Large-scale parallel tempering classical Monte-Carlo simulations reveal that the origin of the delayed percolation transition lies in the frustration of ferromagnetic polarons via competing (anti-)ferromagnetic interactions. Our simulations explicitly show how frustrated polarons act as seeds of the observed magneto-electronic phase separated glassy state at intermediate doping 0.05 < x < 0.18, providing a consistent microscopic understanding across the full doping range.