New multiferroics based on Eu_xSr_1-xTiO₃ nanotubes and nanowires

Abstract

Using Landau-Ginzburg-Devonshire theory, we have addressed the complex interplay between structural antiferrodistortive order parameter (oxygen octahedron rotations), polarization and magnetization in Eu_xSr_1-xTiO₃ nanosystems. We have calculated the phase diagrams of Eu_xSr_1-xTiO₃ bulk, nanotubes and nanowires, which include the antiferrodistortive, ferroelectric, ferromagnetic, and antiferromagnetic phases. For Eu_xSr_1-xTiO₃ nanosystems, our calculations show the presence of antiferrodistortive-ferroelectric-ferromagnetic phase or the triple phase at low temperatures (≤10 K). The polarization and magnetization values in the triple phase are calculated to be relatively high (∼50 μC/cm² and ∼0.5 MA/m). Therefore, the strong coupling between structural distortions, polarization, and magnetization suggests the Eu_xSr_1-xTiO₃ nanosystems as strong candidates for possible multiferroic applications.