Reversible out-of-plane to in-plane magnetic transition by electrical and thermal cycling in Ni_90Fe_10/BaTiO_3(001)

The study investigates the manipulation of the magnetic anisotropy in a thick (1 μm) Ni_90Fe_10 layer electrodeposited on a ferroelectric BaTiO_3(001) substrate, using a combination of Magneto-optical Kerr Effect, Photoemission Electron Microscopy with X-ray circular magnetic dichroism and X-ray diffraction. In the as-grown state, the system shows weak perpendicular magnetic anisotropy and characteristic stripe domains. Upon out-of-plane electrical poling of the BaTiO_3 substrate, the magnetic anisotropy switches to in-plane with a strong uniaxial behavior. This change is ascribed to the magnetoelastic effect due to the switching of the BaTiO_3 ferroelectric [001] axis into the sample plane, as evidenced by XRD. The strong mechanical interaction with the thick Ni_90Fe_10 overlayer prevents the full inversion of the substrate. The perpendicular magnetic anisotropy can be recovered by a mild thermal annealing above the BaTiO_3 tetrahedral to cubic phase transition and can be cycled by repeated electrical poling/thermal annealing. This method opens the path to a reversible control of the magnetic anisotropy in Ni_90Fe_10/BaTiO_3 heterostructures from perpendicular to in-plane.