Anisotropic magnetoconductance and Coulomb blockade in defect engineered Cr2Ge2Te6 van der Waals heterostructures

We demonstrate anisotropic tunnel magnetoconductance by controllably engineering charging islands in the layered semiconducting ferromagnet ${\mathrm{Cr}}₂{\mathrm{Ge}}₂{\mathrm{Te}}₆$. This is achieved by assembling vertical van der Waals heterostructures comprised of graphene electrodes separated by crystals of ${\mathrm{Cr}}₂{\mathrm{Ge}}₂{\mathrm{Te}}₆$. Carefully applying vertical electric fields in the region of $(E\ensuremath{\sim}25$--50 mV/nm) across the ${\mathrm{Cr}}₂{\mathrm{Ge}}₂{\mathrm{Te}}₆$ causes its dielectric breakdown at cryogenic temperatures. This breakdown process has the effect of introducing subgap defect states within the otherwise semiconducting ferromagnetic material. Low-temperature electron transport through charging islands reveals Coulomb blockade behavior with a strongly gate-tuneable anisotropic magnetoconductance, which persists up to $T\ensuremath{\sim}60$ K. We report average tunnel magnetoresistance values of $100%$. This work opens new avenues and material systems for the development of nanometer-scale electrically controlled spintronic devices.