Electric field control of anisotropy and magnetization switching in CoFe and CoNi thin films for magnetoelectric memory devices

We report on the marked change in magnetic anisotropy and magnetization reversal in Co50Fe50/[Pb(Mg1/3Nb2/3O3)]1−x-[PbTiO3]x (PMN-PT) and Co43Ni57/PMN-PT heterostructures under an electric field. For the Co50Fe50/PMN-PT structure, the electric-field-induced magnetic anisotropy field can be as large as 1.2 kOe at 12 kV/cm, corresponding to a magnetoelectric coefficient of 100 Oe cm/kV. In the Co43Ni57/PMN-PT heterostructure, the electric-field-induced anisotropy has a sign opposite to that in Co50Fe50/PMN-PT. As a result, in the [CoNi/Cu/CoFe/Cu]n/PMN-PT heterostructure, the parallel magnetic moment between two magnetic layers in the initial state may become perpendicular under an electric field. On the basis of these discussions, a voltage-write magnetoelectric memory device model is proposed.