Prediction of a multiferroic state with large electric polarization in tensile-strained TbMnO3

By performing first-principles calculations, we systematically explore the effect of epitaxial strain on the structure and properties of multiferroic TbMnO3. We show that, although the unstrained bulk TbMnO3 displays a noncollinear antiferromagnetic spin order, TbMnO3 can be ferromagnetic under compressive strain, in agreement with the experimental results on TbMnO3 grown on SrTiO3. By increasing the tensile strain up to 5%, we predict that TbMnO3 transforms into a multiferroic state with a large ferroelectric polarization, two orders of magnitude larger than that in the unstrained bulk, and with a relatively high Neel temperature E-type antiferromagnetic order. We also find that the ferroelectric domain and antiferromagnetic domain are interlocked with each other, thus an external electric field can switch the ferroelectric domain and the antiferromagnetic domain simultaneously. Our work demonstrates that strain engineering can be used to improve the multiferroic properties of TbMnO3.