First-principles study on the phase diagram and multiferroic properties of (SrCoO3)1/(SrTiO3)1 superlattices

To design a multiferroic material at atomic scale, strong spin-lattice and charge-lattice couplings play crucial roles. Our first-principles calculation on (SrCoO3)1/(SrTiO3)1 superlattices, with above coupling properties, yields a rich physical phase diagram as a function of epitaxial strain. In particular, a robust ferroelectric ferromagnetic insulator of Pc symmetry is stabilized at tensile strain Δa/a0 = 0.86%-5.53%. The polarization can be as large as 36 μC/cm(2) and magnetic moment can reach 6 μB per unit cell. The magnetocrystalline anisotropy energy (0.16 meV/Co in (001) plane, 0.6 meV/Co in (100) plane) is comparable with that of TbMnO3 compound and the magnetoelectric constant α (1.44 × 10(-3) Gaussian unit) is comparable with that of Co3B7O13Br compound. Our study suggests that epitaxially strained (SrCoO3)1/(SrTiO3)1 superlattices not only offer an excellent candidate for multiferroic materials, but also demonstrate the half-metal and ferromagnetic insulator properties with potential application in spintronic devices.