Electric-field-controlled magnetization reversal in a NiFe/BiFeO3/SrRuO3/SrTiO3 (111) multiferroic heterostructure

Electric-Field-Control of magnetism using BiFeO₃-based heterostructures is attracting a great amount of research interest. BiFeO₃ (BFO) has outstanding ferroelectric properties and G-type antiferromagnetic ordering in the bulk. BFO has also a relatively high ferroelectric Curie temperature (T_C~1100K), high antiferromagnetic Neel temperature (T_N~640K), high remnant polarization (2P_r~110μC/cm²), and low temperature crystallization. Moreover, BFO is the only known multiferroic material which shows both ferroelectric and magnetic ordering above room temperature. Many groups have obtained encouraging results on the E-field control of BFO films. Heron et al. reported a 180 degrees anisotropic magnetoresistance (AMR) phase reversal by an in-plane electric field on BFO film [1]. This result is encouraging to further consideration of the out-of-plane electric field controlled magnetoelectric switching possibilities. However, the room temperature out-of-plane electric field control of magnetism is generally irreversible now [2]. In our study, we try to solve this problem by change the surface orientation. Several times AMR phase reversals have been observed. We try to figure out the reason of this phenomenon.