Interfacial spin glass state and exchange bias in manganite bilayers with competing magnetic orders

TLDR

The study investigates the magnetic behavior of SrMnO₃/La₀.₇Sr₀.₃MnO₃ bilayers, combining G‑type antiferromagnetism with double‑exchange ferromagnetism. The bilayers exhibit a spin‑glass state driven by competing AFM and FM interactions, with the freezing temperature following the Almeida‑Thouless line, exchange bias appearing below this temperature, and the resulting spin frustration generating strong interfacial magnetic anisotropy.

Abstract

The magnetic properties of manganite bilayers composed of G-type antiferromagnetic (AFM) SrMnO${}_{3}$ and double-exchange ferromagnetic (FM) La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ are studied. A spin-glass state is observed as a result of competing magnetic orders and spin frustration at the La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$/SrMnO${}_{3}$ interface. The dependence of the irreversible temperature on the cooling magnetic field follows the Almeida-Thouless line. Although an ideal G-type AFM SrMnO${}_{3}$ is featured with a compensated spin configuration, the bilayers exhibit exchange bias below the spin glass freezing temperature, which is much lower than the N\'eel temperature of SMO, indicating that the exchange bias is strongly correlated with the spin glass state. The results indicate that the spin frustration that originates from the competition between the AFM super-exchange and the FM double-exchange interactions can induce a strong magnetic anisotropy at the La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$/SrMnO${}_{3}$ interface.