2023 年 66 巻 1 号 p. 22-27
Topics related with multiferroic interfaces are discussed from the viewpoint of first-principles electron theory. For the adsorption of 3d transition metals on BaTiO3(001) surfaces, the negatively charged TiO2-terminated surface accommodates transition metals at hollow sites, while the positively charged BaO-terminated surface has transition metals as protrusions. Adsorbed transition metals modify the work function of the substrate remarkably. Furthermore, the feasibility of antisite defects strongly affects the crystal growth of Heusler alloys. For multiferroic interfaces of Heusler alloys on BaTiO3(001), the insertion of a transition-metal atomic layer strongly prevents Si, a multiferroicity killer, from being exposed to interfaces. The magnetoelectric coupling can be enhanced by tuning the composition of the inserted transition-metal atomic layer, where the filling of 3d bands is of importance. Due to strong exchange interaction within the ferromagnetic phase, the control of the magnetization direction can be achieved by the interface magnetic anisotropy.
