Antiferromagnetic coupling of van der Waals ferromagnetic Fe₃GeTe₂

Abstract

Among two-dimensional (2D) layered van der Waals materials, ferromagnetic 2D materials can be useful for compact low-power spintronic applications. One promising candidate material is Fe3GeTe2 (FGT), which has a strong perpendicular magnetic anisotropy and relatively high Curie temperature. In this study, we confirmed that an oxide layer (O-FGT) naturally forms on top of exfoliated FGT and that an antiferromagnetic coupling (AFC) exists between FGT and O-FGT layers. From a first-principles calculation, oxide formation at the interface of each layer induces an AFC between the layers. An AFC causes a tailed hysteresis loop, where two-magnetization reversal curves are included, and a negative remanence magnetization at a certain temperature range.

Tunable Magnetic Anisotropy and Dzyaloshinskii-Moriya Interaction in an Ultrathin van der Waals Fe3GeTe2/In2Se3 Heterostructure

“…As it can be seen in Table 1, the lattice constants of the FGT monolayer agree well with the experimental data (a = 0.4050 nm, b = 0.7014 nm) [33]. Our calculated magnetic moments of the freestanding FGT monolayer are also in agreement with the experimental data (m 1 = 2.18 µ B , m 2 = 1.54 µ B ) [34], which partially proved that our results are reliable.…”

Robust ferromagnetism in wafer-scale monolayer and multilayer Fe3GeTe2

“…Samples are capped unless otherwise stated in the following text (see Methods regarding the capping layer). We note uncapped monolayer and bilayer films did not permit transport measurements due to insulating behavior, likely due to the oxidization of the FGT surface 36 . Differences in transport behavior are negligible between capped and uncapped samples when the thickness ≥ 5 QL (Fig.…”

Unconventional Hall effect and its variation with Co-doping in van der Waals Fe3GeTe2

“…5 f–i). For Co 0.05 FGT and reference FGT, a significant strength of ρ XY U is obtained, larger than THE strength either in vdW material 9 , 18 or other potential skyrmionic FMs 19 , 26 – 32 , 48 , 49 . An increase in x results in a reduction of ρ XY U over the entire temperature range, indicating its sensitivity to the underlying interactions.…”

“…Interestingly, the cusp-like feature and its variation with Co-doping cannot be explained by Stoner-Wohlfarth model 17 or due to planar Hall effect under applied H . Furthermore, owing to the stabilization of pining-type hard magnetic phases in Co x FGT and FGT at much higher temperatures 20 , 48 , the observed behavior is also unlikely to be related to the possibility of incoherent dynamics originating from nucleation and/or motion of magnetic domain walls. Thus, our experimental observations from ρ XY vs. H X and peculiar angular dependencies over the entire range of Co-doping with varying magnetic properties are a strong indication of the existence of an unconventional magnetoresistive feature when H is applied perpendicular to the magnetic easy-axis of the vdW FM.…”