Epitaxial growth and electric control of magnetic behaviors in exchange biased IrMn/FeGa/MgO/PMN-PT heterostructures

We grew exchange biased (001)-textured IrMn/epitaxial FeGa bilayers on ferroelectric PMN-PT(001) substrate with assistance of an MgO buffer layer and investigated the electric control of magnetic behaviors. The as-grown sample exhibits square, asymmetrically shaped, and two-step loops at different magnetic field orientations due to the combined effect of the intrinsic magnetocrystalline anisotropy and the collinear uniaxial and unidirectional magnetic anisotropies, which can be interpreted by the magnetization reversal of domain wall nucleation. After polarized by an electric field, another kind of asymmetrically shape loops with three steps in the descending and two steps in the ascending branch is additionally observed because the uniaxial magnetic anisotropy is greatly enhanced and becomes perpendicular to the exchange bias. The angular dependent magnetic behavior suggests the exchange bias is slightly rotated by the electrically induced strain. The electric field dependence of coercive field and uniaxial magnetic anisotropy exhibit an asymmetrical butterfly-like shape, indicating a strain-mediated magnetoelectric coupling with a net 109° polarization switching of PMN-PT.