First-principles study on strain-controllable magnetoelectric coupling behaviour of two-dimensional BaTiO3 (001) ultrathin film with surface Ba vacancy

A first-principles approach was utilized to investigate the magnetoelectric coupling behaviour of two-dimensional BaTiO3 (001) ultrathin films with surface Ba vacancy under different strains. The total magnetic moment was suppressed when compressive strains were employed and had minimum values of 1.715 mu B and 1.568 mu B corresponding to uniaxial and biaxial strains, respectively; moreover, it exhibits an enhancement in the case of tensile strain. For shear strain, the magnetic moment fluctuated at similar to 1.78 mu B. Furthermore, all partial magnetic moments and spontaneous polarization were functions of the strains except for the case of shear strain. Their conversion efficiency exhibited a regular varying tendency with increasing tensile strain. To explore electron spins, which can also be regulated, spin-orbit coupling calculations were carried out, showing that the changes in partial magnetic moments increased when the tensile strain was enhanced. Our study may pave a way for twodimensional BaTiO3 to be applied in novel spin-based devices.