Effect of surface inhomogeneities on crystalline structure and magnetic properties of epitaxial Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3 film on (001) SrTiO3

Epitaxil Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3 (PSMO/LCMO) bilayer structure was grown on (001)-oriented SrTiO3 (STO) substrate by pulsed laser deposition. High-resolution synchrotron X-ray diffraction showed high quality of epitaxial layer. However, besides diffraction peaks from PSMO layer, LCMO layer and STO substrate, we observed an additional shoulder peak, which might stem from the inhomogeneities of composition in the film. Grazing incidence X-ray reflectivity (GIXRR) was employed to investigate the surface and interfacial crystalline structure of PSMO/LCMO. The fitting results of GIXRR indicated negligible interdiffusion and roughness at interface. Further atomic force microscopy measurement showed the presence of non-stoichiometric large particulates at surface, imparting an overall inhomogeneous composition to the film. This implied that the variation of crystalline structure of PSMO/LCMO film occurred due to inhomogeneous composition. Moreover, studies on magnetic properties showed that surface inhomogeneities and ferromagnetic clusters at the PSMO/LCMO interface probably influenced the ferromagnetism of the bilayer film together, tuning exchange bias in the film.