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

Abstract

We demonstrate anisotropic tunnel magnetoconductance by controllably engineering charging islands inthe layered semiconducting ferromagnet Cr2Ge2Te6. This is achieved by assembling vertical van der Waalsheterostructures comprised of graphene electrodes separated by crystals of Cr2Ge2Te6. Carefully applyingvertical electric fields in the region of (E∼25–50 mV/nm) across the Cr2Ge2Te6causes its dielectric breakdownat cryogenic temperatures. This breakdown process has the effect of introducing subgap defect states withinthe otherwise semiconducting ferromagnetic material. Low-temperature electron transport through chargingislands reveals Coulomb blockade behavior with a strongly gate-tuneable anisotropic magnetoconductance,which persists up toT∼60 K. We report average tunnel magnetoresistance values of 100%. This work opensnew avenues and material systems for the development of nanometer-scale electrically controlled spintronicdevices.