Polarization fatigue of BiFeO3 films with ferromagnetic metallic electrodes

BiFeO3 (BFO) thin films were epitaxially grown on (001) SrTiO3 substrates using LaNiO3 as bottom electrode by pulsed laser deposition. The ferroelectric properties of BFO layer with ferromagnetic Ni21Fe79 (NiFe) or non-magnetic Pt electrode are investigated. Well saturated polarization-electric field (P-E) hysteresis loops are observed. Significant fatigue and associated drastic decrease in switchable polarization have been observed with cycling number exceeds 106, which can be explained by the domain wall pinning due to the oxygen vacancies trapping. With increasing cycle number to above 107, the polarization is rejuvenated. The polarization for BFO layer with NiFe electrode recovers to the initial value, while only about 75% of initial polarization is recovered for BFO layer with Pt electrode. Furthermore, the imprint is alleviated and the P-E hysteresis loops become more symmetric after the polarization recovery. The difference can be understood by the different interface state of NiFe/BFO and Pt/BFO.