Evolution of the charge- and strain-mediated magnetoelectric coupling effect in the La0.7Sr0.3MnO3/BaTiO3 bilayer

The epitaxial La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) bilayer films with various volume fraction v of ferroelectric (FE) phase (BTO) are fabricated on (001) oriented LaAlO3 substrate. The value of v is regulated by changing the thickness of LSMO film, and fixing the thickness of BTO film. The value of v is demonstrated to play a key role in determining the interface magnetoelectric (ME) coupling coefficient (k) of the LSMO/BTO bilayers, i.e. a lower value of v leads to a lower value of k. Furthermore, as v is 0.91, experimental value of the ME voltage coefficient alpha(E) is higher than its calculated value, which indicates that the main ME coupling mechanism have evolved from strain-mediated to charge-mediated. This result can provide an available method for the design of multiferroic composite bilayer films with adjustable ME coupling mechanism by optimizing the volume fraction of FE phase. (C) 2015 Elsevier B.V. All rights reserved.