Manipulating magnetoelectric properties by interfacial coupling in LaSrMnO/BaSrTiO superlattices.

Artificial superlattices constructed with ferromagnetic LaSrMnO layer and ferroelectric BaSrTiO layer were designed and fabricated on SrTiO substrates. An epitaxial growth with sharp interfaces between LaSrMnO and BaSrTiO layers was confirmed by scanning transmission electron microscopy and x-ray diffraction. An unambiguous charge transfer involving an electron transferring from the LaSrMnO layers to BaSrTiO layers (Mn→Mn; Ti→Ti) 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 LaSrMnO and BaSrTiO layers. Huge magnetoresistance subsisting to low temperature was also observed in the LaSrMnO/BaSrTiO 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.