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

Abstract

We demonstrate anisotropic tunnel magnetoconductance by controllably engineering charging islands in the layered semiconducting ferromagnet Cr 2 Ge 2 Te 6 . This is achieved by assembling vertical van der Waals heterostructures comprised of graphene electrodes separated by crystals of Cr 2 Ge 2 Te 6 . Carefully applying vertical electric fields in the region of (E ∼ 25-50 mV/nm) across the Cr 2 Ge 2 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 ∼ 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.

Van der Waals ferromagnetic Josephson junctions

“…Josephson frequency equals the eigenfrequency of electromagnetic oscillations in this cavity, proving a well-defined JJ through the vdW stacking. Returning to the cavity nature of our JJ, the specific capacitance C s can be also derived from the first voltage position V 1 (0.57 mV) of the Fiske steps and the plasma frequency ω p , calculated as 22.3–26.9 fF μm −2 which has the similar magnitude as obtained for Cr 2 Ge 2 Te 6 32 ( C s ~5.5–21.8 fF μm −2 , the dielectric constant ε is ~4–16). And the parameter β c is given by the relationship as 5.4–6.7, larger than the estimation using the RCSJ model due to thermal activation or noises in the external circuits of IV measurements 33 , making it complicated to evaluate the internal dissipation.…”

Polaronic Conductivity in Cr2Ge2Te6 Single Crystals

“…[ 1 ] The mechanism of intrinsic long‐range magnetic order in monolayers of 2D materials such as CrI 3 and bilayer Cr 2 Ge 2 Te 6 might be exploited for design of novel spin‐related devices. [ 2,3 ] They can be stacked into heterostructures [ 4–9 ] and their physical properties are highly tunable by carrier doping, [ 10–13 ] strain, [ 14–16 ] vacancies, [ 17–21 ] pressure, [ 22–26 ] and electric field. [ 27–30 ]…”

“…[1] The mechanism of intrinsic long-range magnetic order in monolayers of 2D materials such as CrI 3 and bilayer Cr 2 Ge 2 Te 6 might be exploited for design of novel spin-related devices. [2,3] They can be stacked into heterostructures [4][5][6][7][8][9] and their physical properties are highly tunable by carrier doping, [10][11][12][13] strain, [14][15][16] vacancies, [17][18][19][20][21] pressure, [22][23][24][25][26] and electric field. [27][28][29][30] Cr 2 Ge 2 Te 6 exhibits a paramagnetic (PM) to ferromagnetic (FM) transition with the Curie temperature (T c ) of ≈61-68 K in bulk, an out-of-plane easy axis and negligible coercivity.…”

Temperature‐Dependent Electronic Transport in Non‐Bulk‐Resistance‐Variation Nitrogen‐Doped Cr2Ge2Te6 Phase‐Change Material

“…The host static dielectric constant of pure crystalline CrGT has been estimated to be 4.0 using the plane plate capacitor model. [ 27 ] Here we applied the same value to the crystalline NCrGT and assumed that the is temperature‐independent between 0 and 300 K. As the hopping behavior of the NCrGT is similar in both amorphous and crystalline phase at low temperature, same was also used in the amorphous NCrGT. Combining Equations ()–() yields the relation between Δ CG, N ( E F ) and ε [ 28 ] …”