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

The magnetic properties of manganite bilayers composed of G-type antiferromagnetic (AFM) SrMnO₃ and double-exchange ferromagnetic (FM) La0.7Sr0.3MnO₃ are studied. A spin-glass state is observed as a result of competing magnetic orders and spin frustration at the La0.7Sr0.3MnO₃/SrMnO₃ interface. The dependence of the irreversible temperature on the cooling magnetic field follows the Almeida-Thouless line. Although an ideal G-type AFM SrMnO₃ 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 La0.7Sr0.3MnO₃/SrMnO₃ interface.