Manipulating magnetoelectric properties by interfacial coupling in La_0.3Sr_0.7MnO₃/Ba_0.7Sr_0.3TiO₃ superlattices

Artificial superlattices constructed with ferromagnetic La_0.7Sr_0.3MnO₃ layer and ferroelectric Ba_0.7Sr_0.3TiO₃ layer were designed and fabricated on SrTiO₃ substrates. An epitaxial growth with sharp interfaces between La_0.7Sr_0.3MnO₃ and Ba_0.7Sr_0.3TiO₃ layers was confirmed by scanning transmission electron microscopy and X-ray diffraction. An unambiguous charge transfer involving an electron transferring from the La_0.7Sr_0.3MnO₃ layers to Ba_0.7Sr_0.3TiO₃ layers (Mn³⁺→Mn⁴⁺; Ti⁴⁺→Ti³⁺) across the interface were resolved by electron energy loss spectra analysis. These observations are attributed to the possible modification in the stereochemistry of the Ti and Mn ions in the interfacial region. The out-of-plane lattice parameter, Curie temperature, and magnetoresistance are strongly affected by the thicknesses of the La_0.7Sr_0.3MnO₃ and Ba_0.7Sr_0.3TiO₃ layers. Huge magnetoresistance subsisting to low temperature was also observed in the La_0.7Sr_0.3MnO₃/Ba_0.7Sr_0.3TiO₃ superlattices. All spectral changes identified at a nanometer scale and their potential effect on the degradation of magnetic and transport properties at a macroscopic level. These findings highlight the importance of dependence on sublayer thickness, illustrating the high degree of tenability in these artificially low-dimensional oxide materials.