Voltage-Controlled Switching of Magnetic Anisotropy in Ambipolar Mn2CoAl/Pd Bilayers

Abstract

An ultrahigh electric field induced by ionic liquid gating (ILG) can be employed to manipulate ferromagnetism with low Joule heating dissipation, showing great potential for spintronics applications. In ferromagnetic/heavy metal thin films, however, typical materials used in both layers are electron-carrier dominant, which significantly suppresses the ILG effect due to the short electrostatic screening length in metal. Here, we employ ${\mathrm{Mn}}_{2}\mathrm{Co}\mathrm{Al}$, a spin gapless semiconductor with hole carriers, as the ferromagnetic layer and investigate the ILG effect in $\mathrm{Mg}\mathrm{O}/{\mathrm{Mn}}_{2}\mathrm{CoAl/Pd}$ ultrathin films with perpendicular magnetic anisotropy. Reversible change of the magnetic anisotropy from the out-of-plane to the in-plane direction is achieved, induced by electrostatic charge accumulation. Moreover, ambipolar transport behavior has been observed and explained by a two-carrier model. Finally, we find that skew scattering is the mechanism of the anomalous Hall effect and can be enhanced at a positive gate voltage in our system. Our results strongly demonstrate that a significant ILG effect on magnetism can be easily achieved in two-carrier dominant ultrathin films.