Exchange bias and crystal structure of epitaxial (111) FePt/BiFeO3 sputtered thin films

Crystallographic structure and magnetic properties of the epitaxial FePt (10 nm)/BiFeO3 (BFO) (10 nm) bilayer films grown on (111) SrTiO3 (STO) substrates with different deposition temperatures of FePt layers (Td) have been investigated using magnetron sputtering. Out-of-plane radial scan along (111) direction and off-normal (002) azimuthal scan, determined by synchrotron radiation x-ray diffractometry, evidence that the FePt layers were well epitaxially grown on the (111) epitaxial BFO layers for the samples with Td = 300 and 700 °C. On the contrary, for the bilayer films with Td = 500 °C, the FePt and BFO layers exhibit low epitaxial quality. Large in-plane exchange bias field (Heb) values of 45–412 Oe are obtained for the L10-FePt/BFO bilayer films measured with applied field of 12 kOe at room temperature. The change of effective interfacial area, observed by scanning electron microscopy, between FePt island-like particles and BFO continuous layers, and epitaxiality of the bilayer were correlated with the evolution of Heb