Electric field tunable anisotropic magnetoresistance effect in an epitaxial Co 2 Fe Si / Ba Ti O 3 interfacial multiferroic system

We study magnetic and magnetotransport properties of an epitaxial interfacial multiferroic system consisting of a ferromagnetic Heusler-alloy ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ and a ferroelectric-oxide $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$. $L{2}_{1}$-ordered ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ epilayers on $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ show an in-plane uniaxial magnetic anisotropy with strong temperature dependence, induced by the presence of the magnetoelastic effect via the spin-orbit interaction at the ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}/\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ interface. In the ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ Hall-bar devices, the anisotropic magnetoresistance (AMR) hysteretic curves depending on in-plane magnetization reversal processes on the $a$ and $c$ domains of $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ are clearly observed at room temperature. Notably, the magnitude of the AMR ratio (%) for ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}$ Hall-bar devices can be tuned through the $a\ensuremath{-}c$ domain wall motion of $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ by applying electric fields. We propose that the tunable AMR effect is associated with the modulation of the spin-orbit interaction, exchange interaction, and/or the electronic band structure near the Fermi level by applying electric fields in the epitaxial ${\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Si}/\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}(001)$ interfacial multiferroic system.