Spontaneous positive exchange bias effect in SrFeO_(3-x)/SrCoO_(3-x) epitaxial bilayer

摘要

A novel phenomenon of spontaneous positive exchange bias(PEB)is reported in SrFeO_(3-x)/SrCoO_(3-x) epitaxial bilayer without undergoing any magnetic field treatment.When inserting a thick SrTiO3(STO)nonmagnetic spacer(about 6 nm)into the bilayer interface,this phenomenon still exists.Based on a series of testing means,the spontaneous PEB effect is supposed to be mainly related to short-range ferromagnetic(FM)exchange coupling at the interface when there is no STO spacer.As the STO interlayer reaches up to a certain thickness,shortrange coupling interaction basically disappears.At this time,the long-range dipole field may be responsible for the coupling of the FM and antiferromagnetic(AFM)layer across the nonmagnetic STO and then leads to the same bias effect.Our discoveries provide a new way to realize and manipulate spontaneous exchange bias-based spintronics devices,such as magnetic recording heads and spin valves.