Tailing Magnetoelectric properties of Cr2Ge2Te6 by Engineering Covalently bonded Cr Self-intercalation: Ferromagnetic Half-metal

Abstract: Two-dimensional intrinsic ferromagnetic half-metal (HM) are important for the spintronics. Manipulating the interlayer magnetic coupling of van der Waals magnetic materials is an important method to control magnetoelectric properties, which is especially useful for the spintronics. Here, based on systematical research of CrGeTe3 (CGT) bilayer and multilayers with s of self-intercalated (SI) Cr atom, we find that self-intercalation can enhance the interlayer magnetic coupling. The super-exchange interaction still dominates interlayer magnetic exchange interaction, which results in ferromagnetic coupling between neighboring vdW layers. CGT bilayer keeps HM with FM order after Cr self-intercalation, independent of self-intercalated Cr (CrSI) atoms' concentration. Most importantly, self-intercalated CrGeTe3 (SI-CGT) bilayers show ferromagnetic HM, independent of stacking orders. Moreover, SI-CGT multilayers keep FM order, independent of films' thickness. However, SI-CGT multilayers transform from HM into normal spin-polarized metal, as the states at the Fermi-level increases. Moreover, magnetic anisotropy energy (MAE) of SI-CGT-AA and SI-CGT-AB are -0.160 and -0.42 meV/.f.u., which are modulated by CrSI atoms. The MAE of SI-CGT-AA and SI-CGT-AB are different, as the hybridization interaction between Cr's d orbitals is different. SI-CGT multilayers' magnetic easy axis (EA) switches from [001] of CGT to [100] direction, independent of stacking orders. It origins that MAE mainly contributed by hybridization between Te atoms' px and py, py and pz orbitals is obvious weakened as CrSI is introduced. SI-CGT multilayers show good dynamical, thermal, and magnetic stability at 300 and 500 K. These findings find a promising way to manipulate interlayer exchange interaction and magnetoelectric properties of CGT multilayers and other vdW magnets.