Large magnetoelectric effect in the strained CoPt/SrTiO3 junction

Abstract

The intrinsic critical thickness for the ferroelectricity and magnetoelectric effect in the strained CoPt/SrTiO3 junction is investigated using first-principles based on the density functional theory. We found that the ferroelectric polarization can be maintained in about 12 Å thick SrTiO3 films when the compressive strain is up to 3.82%. The critical thickness can be as small as the value of the CoPt/BaTiO3 junction under the same strain. The small critical ferroelectric thickness for the SrTiO3 film is due to the screening effect of interfacial charges. The magnetoelectric effect is determined by the difference in the magnetic moments of interfacial atoms when the electric polarization reverses. The underlying physics is the changes in the interface bonding which can significantly alter the interfacial electronic hybridizations. Furthermore, the effect of different misfit strains on the ferroelectric properties and magnetoelectric coupling of the CoPt/SrTiO3 film is also studied. It is found that the ferroelectric polarization and magnetoelectric effect are enhanced as the compressive strain increases. The strained paraelectric/ferromagnetic junction opens a direction to design novel nanometer-scale electronic and spintronic devices.