Electrical switching of magnetization in the artificial multiferroic CoFeB/BaTiO_3

Abstract

Electronic, magnetic, chemical, and mechanical phenomena occurring in metal/oxide heterostructures have recently received great attention in view of their exploitation in novel solid state devices. In particular, artificial multiferroics, i.e., layered or composite systems made of a ferromagnetic and ferroelectric phase, hold potential for achieving the electric control of the magnetization in spintronic devices. In this paper, a novel artificial multiferroic displaying perpendicular magnetic anisotropy is reported: the CoFeB/BaTiO3 bilayer. At room temperature, the CoFeB magnetic coercive field displays a hysteretic behavior, as a function of the voltage across the BaTiO3 layer, with a 60% variation for complete reversal of the ferroelectric BaTiO3 polarization. This is exploited to achieve the electric switching of the magnetization of individual CoFeB electrodes under a uniform magnetic bias field. Upon the local BaTiO3 polarization reversal, the CoFeB electrode jumps from an initial metastable state into the opposite stable magnetization state, with a characteristic switching time determined by magnetic viscosity. The magnetically assisted bipolar electric switching of the magnetization is demonstrated, via voltage pulses compatible with complementary metal-oxide semiconductor (CMOS) electronics, under uniform bias fields as low as 10 Oe.