Role of Oxygen 2p states for anti-ferromagnetic interfacial coupling and positive exchange bias of ferromagnetic LSMO/SRO bilayers

We have investigated possible physical origins of the anti-ferromagnetic exchange interaction of ferromagnetic La2/3Sr1/3MnO3/SrRuO3 (LSMO/SRO) bilayers reported to have a positive exchange bias. We have performed first principles calculations with both ferro, and anti-ferromagnetic spin configurations for these layers and found that anti-ferromagnetic spin configuration has lower total energy. The role of 2p states of oxygen atoms located at the interface and their interaction with neighbors account for this magnetic ordering preference.