November 07, 2022
Minneapolis, United States
Unconventional Emergent Hall Effect Phenomena and its Modification In a van der Waals Ferromagnet Fe3GeTe2
Magnetism in two-dimensional (2D) van der Waals (vdW) materials has emerged as a new paradigm enunciating new condensed matter phenomena, bearing potential for application in future spintronic and quantum computing devices (1,2). Among 2D vdW ferromagnets (FMs), metallic Fe3GeTe2 (FGT) is interesting owing to its high Curie temperature, uniaxial magnetic anisotropy, existence of unusual magnetic ground state. An understanding of factors responsible for unconventional magnetism and associated magnetoresistive manifestations has remained elusive. Here, we clarify the underlying physics responsible for nontrivial ground state and demonstrate tuning of emergent properties by substitution at magnetic (Fe) or nonmagnetic (Ge) sites in 2D vdW FGT.
High quality single-crystalline FGT, (Fe1-xCox)3GeTe2, Fe3(Ge1-xAsx)Te2 , (0 ≤ x ≤ 1) were grown by chemical vapor transport method. Magnetotransport measurements under H || c-axis result in sizeable anomalous Hall effect, arising from topological nodal lines in the band structure. Interestingly, transverse resistivity under H ⊥ c-axis result in unconventional magnetoresistive behavior with prominent cusp-like feature (Fig. 1) (3,4). Concomitant magneto-optical imaging indicates emergent skyrmion lattice-like structure, size varying with doping and angular magnetotransport confirms their 2D nature. Separation of magnetoresistive responses indicates dominant unconventional emergent Hall effect (3,4), tunable with magnetic or non-magnetic doping (Fig. 2), significantly larger than in other vdW, skyrmion-hosting materials (5-7). Our results deepen understanding of emergent responses from complicated spin textures prospective for topological magnetism and non-collinear spin texture-based spintronic devices.
RRC acknowledges DST for financial support (DST/INSPIRE/04/2018/001755). We thank H. Ohno for discussions. This work is partly supported by RIEC Cooperative Research Project.
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