The surface and interface microstructure of epitaxial Pr_(0.7)Sr_(0.3)MnO_3/La_(0.5)Ca_(0.5)MnO_3 bilayer structure

摘要

Epitaxial bilayer structure consisting of ferromagnetic (FM) metallic Pr_(0.7)Sr_(0.3)MnO_3 (PSMO) and antiferromagnetic (AFM) insulator La_(0.5)Ca_(0.5)MnO_3 (LCMO) was fabricated on (001)-oriented single crystal SrTiO_3 (STO) substrate by pulsed laser deposition technique. We studied the surface structure and interdiffusion at interface between PSMO and LCMO by using atomic force microscope and grazing incident x-ray reflectivity (GIXRR). The perfect data fitting result of GIXRR indicated that interdiffusion at the interface of Pr_(0.7)Sr_(0.3)MnO_3/La_(0.5)Ca_(0.5)MnO_3 (PSMO/LCMO) could not be negligible; there was a large interdiffusion zone at the PSMO/LCMO interfaces with a thickness of about 7 nm. We found that the thickness of the top layer at air/PSMO interface was about 2.5 nm and the mass density of the top layer was about 76.53% of that of PSMO layer. The surface roughness was about 1.6 nm which was consistent with observation by atomic force microscopy. Normal X-ray diffraction (NXRD) was also employed to investigate the average structure. Except from PSMO and LCMO layer diffraction peaks, we observed another additional peak, which was developed from the large disordered layer resulting from interdiffusion at the interface of PSMO/LCMO. This implied that the variation of crystalline structure of PSMO/LCMO film occurred due to interdiffusion. Surface roughness and interdiffusion played an important role in magnetic properties of FM/AFM bilayer.