Anomalous Hall effect in the van der Waals bonded ferromagnet Fe3−xGeTe2

Abstract

We report anomalous Hall effect (AHE) in single crystals of quasi-two-dimensional Fe3−xGeTe2 (x ≈ 0.36) ferromagnet grown by the flux method which induces defects on Fe site and bad metallic resistivity. Fe K-edge x-ray absorption spectroscopy was measured to provide information on local atomic environment in such crystals. The dc and ac magnetic susceptibility measurements indicate a second-stage transition below 119 K in addition to the paramagnetic to ferromagnetic transition at 153 K. A linear scaling behavior between the modified anomalous Hall resistivity ρxy/µ0H ef f and longitudinal resistivity ρ 2 xx M/µ0H ef f implies that the AHE in Fe3−xGeTe2 should be dominated by the intrinsic Karplus-Luttinger mechanism rather than the extrinsic skew-scattering and side-jump mechanisms. The observed deviation in the linear-M Hall conductivity σ A xy below 30 K is in line with its transport characteristic at low temperatures, implying the scattering of conduction electrons due to magnetic disorder and the evolution of the Fermi surface induced by possible spin-reorientation transition.

Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet Fe3GeTe2 through Hole Doping

“…One such observable is the large AHE, 15 induced by the Berry phase from the lifting of the band degeneracy along the K-H lines around the electron pockets. 15 A large AHE is expected when the Fermi energy crosses the electron pockets, consistent with the reported AHE for both pristine and hole doped Fe3GeTe2; 25 the decreased AHE of hole doped Fe3GeTe2 15,25 can be qualitatively understood by the reduced surface area of the electron pockets with hole doping. Our mechanism is also consistent with the voltage induced enhancement of the Tc in ultrathin Fe3GeTe2, 17 in which the increased surface area of electron pockets by electron doping could play an important role.…”

Large Anomalous Nernst Effect in a van der Waals Ferromagnet Fe3GeTe2

“…This places FGT outside the realm of common FM materials. We further found that the temperature dependence of the transverse thermoelectric conductivity αxy follows the Mott relation xy = −( cm -1 ) indicates the origin of the observed large AHE and ANE in FGT is primarily the intrinsic mechanism from the large Berry curvature, and not scattering, such as skew scattering and side-jump [23][24][25], consistent with the topological nature of FGT [12,26].…”

“…The scaling relationship with n = 2 indicates that the intrinsic mechanism or side-jump, instead of skew scattering, dominates AHE and ANE [23][24][25] in FGT. Previous reports have shown the intrinsic mechanism dominates AHE in FGT [12,26], therefore n close to 2 favors intrinsic mechanism in FGT. At the same time, the anomalous Hall conductivity is xy ≈ 360~400 Ω -1 cm -1 at low temperature, which is close to the intrinsic contribution xy,in ≈ 2 /ℎ z ≈ 470 Ω -1 cm -1 ,…”

A van der Waals antiferromagnetic topological insulator with weak interlayer magnetic coupling

“…c) presents the field-cooled (FC) magnetic susceptibility data of (H ∥ ab) and(H || c) measured at 0.1 T. The abrupt halt in the rise of on cooling suggests the onset of AFM ordering, similar to that seen in the other vdW antiferromagnets MnBi2Te4 and CrCl3,9,18,21 but different from the FM one22 , suggesting that long range AFM ordering takes place at 12 K. Fitting the susceptibilities up to 80 K to the Curie-Weiss law results in Weiss temperatures of = 11.5 K, = 12.2 K, = 11.7 K, and5 Mn. These values suggest magnetic isotropy above TN and thus negligible single ion anisotropy in the material.…”