Antiferromagnetic LaFeO3 thin films and their effect on exchange bias

Abstract

Antiferromagnetic (AFM) orthoferrites are interesting model systems forexploring the correlation between their crystalline and AFM domains and theresulting exchange bias when coupled to a ferromagnetic layer. In particular,LaFeO3 (LFO) has a Néeltemperature, TN = 740 K, which is the highest in the orthoferrite family. The recent developments of synchrotronradiation-based photoelectron emission microscopy (PEEM) have provided the possibilityof studying AFM domain structures as well as the magnetic coupling between the AFMand the adjacent ferromagnetic (FM) layer, domain by domain. Thin films of LFOhave proved excellent candidates for such studies because their AFM domainsare well defined and large enough to be readily imaged by PEEM. This paperreviews the growth, structural and magnetic properties of LFO thin films as well asexchange coupling to a FM layer. The strong correlation between structural andAFM domains in this material allows us to investigate the exchange coupling as afunction of the domain configuration, which can be changed by using differentsubstrate material and substrate orientation. A significant increase of the exchangebias field by a factor of about 10 was obtained when LFO was diluted with Niatoms in the volume part. In this sample, the structural domain boundary becamecorrugated due to substitutional defects. Our results indicate that the details of theprecise domain boundary configuration strongly affect the exchange coupling.