Stability of spin-driven ferroelectricity in the thin-film limit: Coupling of magnetic and electric order in multiferroic TbMnO_3 films

摘要

We demonstrate spin-spiral-induced ferroelectricity in epitaxial TbMnO_3 films grown on YAlO_3 substrates down to a film thickness of 6nm. The ferroelectric polarization is identified by optical second-harmonic generation. Using x-ray resonant magnetic scattering we directly prove the existence of a noncollinear magnetic structure in the ferroelectric phase and thus bulk-like multiferroicity. The electric-field-induced reversal of the magnetic domains along with the reversal of the ferroelectric polarization evidences the rigid coupling of magnetic and ferroelectric order and hence a "giant" magnetoelectric effect in the films.