Electric field control of magnetism in FePt/PMN-PT heterostructures

Abstract

Laminar heterostructures composed by materials with different ferroic properties have been proposed for the control of magnetism with an applied voltage. We present here a study of the structural and magnetic properties of chemically disordered FePt ferromagnetic films of different thicknesses that have been sputter-deposited on ferroelectric PMN-PT (011) single crystals. By means of static and dynamic magnetic measurements we have found that it is possible to switch the magnetization easy axis by 90° if an electric field is applied in a direction perpendicular to the film plane. Using ferromagnetic resonance techniques we have estimated the strain induced magnetoelectric coupling of the FePt/PMN-PT heterostructure, obtaining ME=477(15) Oe m/MV for FePt thicknesses greater than 26 nm, which corresponds to an average magnetoelastic constant B=−13.2(1.1) MJ/m3. The associated saturation magnetostriction was estimated in λs∼90 ppm. Films thinner than 26 nm present corresponding values that are smaller by approximately 20%. A possible explanation for this difference is the well known transition from planar to stripe-like magnetic domains that occurs in FePt around this film thickness. However, this thickness dependence of ME is relatively smaller than that found in other ferromagnets such as Fe or FeGa, which makes FePt a potential candidate for thin film applications in magnetoelectronic devices.