The exchange bias in polycrystalline BiFeO3/Ni81Fe19 bilayers on Si substrate with LaNiO3 buffer layer

Single phase polycrystalline BiFeO3 thin films have been grown on Si substrates using LaNiO3 as buffer layers by pulsed laser deposition. A transmission electron microscope shows an amorphous thin layer of LaNiO3 followed by the polycrystalline LaNiO3, which facilitates the crystallization of a BiFeO3 layer in R3c structure and suppression of the impurity phases. NiFe layers were deposited on the BiFeO3 layer by magnetron sputtering. Clear exchange coupling between BiFeO3 and NiFe (with maximum exchange bias field up to 61 Oe) has been observed at room temperature, and the exchange bias field decreases with increasing the NiFe thickness. Our results clearly demonstrate the potential application of polycrystalline BiFeO3 in magnetoelectric coupling based spintronics.