Interfacial spin glass mediated spontaneous exchange bias effect in self-assembled La0.7Sr0.3MnO3:NiO nanocomposite thin films

Abstract

Zero field cooled spontaneous exchange bias (SEB) is observed in self-assembled nanocomposite thin films of La0.7Sr0.3MnO3 (LSMO):NiO grown on single crystal line SrTiO3 (001) substrate by pulsed laser deposition. SEB is displayed by the asymmetry in the hysteresis loop of the composite film along with the field cooled conventional exchange bias (CEB) effect. The training effect shows that exchange bias relaxation is disorder mediated. It is revealed from DC magnetization measurements that such nanocomposite film divulges spin glass like behaviour, arising due to competing ferromagnetic and antiferromagnetic interactions at the assorted interfaces of ferromagnetic LSMO and antiferromagnetic NiO. X-ray magnetic circular dichroism (XMCD) measurements discern that SEB is mainly originating due to ferromagnetic coupling of unstable interfacial antiferromagnetic spin due to NiO with the ferromagnetic LSMO at the disordered interface. These results of self-assembled thin films provide a useful input to realize and understand microscopic origin of SEB for device application.