Quantifying electric-field control of magnetization rotation in Ni/SiO2/Ti/(011)-PMN-PT multiferroic heterostructures via anisotropic magnetoresistance measurements

We report that magnetization switching behaviors in multiferroic Ni/SiO2/Ti/(011)-PMN-PT hetrostructures with Hall-bar geometry can be easily understood by measuring angle-dependent anisotropic magnetoresistance (MR). The MR along the in-plane [100] and [011¯] directions of the Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrate were −0.175% and 0.165% at 200 Oe, respectively. The coercive field along the in-plane [100] and [011¯] directions of the PMN-PT substrate were both increased from 30 Oe at 0 kV/cm to 75 Oe at 4 kV/cm. However, we observed the anisotropic tunability of the AMR in this multiferroic heterostructure. While the AMR with magnetic field H (~200 Oe) parallel to j was 0.165% at the zero electric field and decreased to 0.032% at 4 kV/cm, the AMR with H perpendicular to j increased from −0.174% at the zero electric field to −0.339% at 4 kV/cm. Furthermore, based on angle-dependent AMR measurements using rotating in-plane external magnetic fields, the easy axis was determined to lie along the [011¯] direction and was rotated 15° by the 4 kV/cm electric field. Our work provides a facile method to study magnetization switching behaviors in multiferroic heterostructures by measuring angle-dependent AMR.