The effect of interface strains induced by various ferroelectric top layers on the magnetoelectric behavior for bilayer heterostructure

Using PLD technique, highly c-axis oriented bilayer heterostructures based on ferromagnetic La_0.7Sr_0.3MnO₃ (LSMO) have been epitaxially grown on (001) oriented LaAlO₃ (LAO) substrates with ferroelectric layers of PbZr_0.52Ti_0.48O₃ (PZT) or BaTiO₃ (BTO). The interface strain values at the top of LSMO are influenced by distinct ferroelectric top layers, which results in a slightly weaker saturation magnetization strength in the PZT/LSMO heterostructure than that in the BTO/LSMO heterostructure. The correlation between the frequency of the AC excitation magnetic field and the variation of the ME voltage coefficient (α_E) indicates that both heterostructures present strong room-temperature dynamic ME coupling behavior. The α_E value increases rapidly with increasing frequency before stabilizing. These two bilayer multiferroic heterostructures also exhibit the self-biased ME coupling effect, as demonstrated by the variations in the α_E value with the DC bias magnetic field strength.