The discovery of type-II Weyl semimetal states in layered transition metal dichalcogenides Td-WTe 2 indicates great potential for novel electronic, spintronic, and quantum devices. Theoretically, the interaction between the topological states and the magnetic ordered states of Td-WTe 2 enables the modulation of Weyl semimetal states by an external magnetic field. However, currently, ferromagnetism in layered Td-WTe 2 is still elusive and rarely observed. In this research, ferromagnetic order into WTe 2 using magnetic chromium (Cr) doping with a two-step Te flux strategy is introduced. The Curie temperature ( T c ) and the ferromagnetic moment are well tuned with a Cr doping concentration. The T c of the Cr-doped layered Td-WTe 2 could be regulated from 182 to 283 K, which is close to room temperature. The saturation magnetic moment could be changed from 2.26 to 4.20 emu g –1 , which is stronger than most values reported for these materials. Most intriguingly, the Cr-doped layered Td-WTe 2 single crystals still exhibit semimetallic behavior and they possess very large magnetoresistance with obvious Shubnikov de Haas (SdH) quantum oscillations and an anomalous Hall effect. The findings offer feasible ways to induce and tune ferromagnetic orders in layered Td-WTe 2 and thus to control its topological phase with external magnetic fields.
Mingkun Zheng,Wancheng Zhang,You Lv,Yong Liu,Rui Xiong,Zhenhua Zhang,Zhihong Lu
The low-symmetry Weyl semimetallic Td-phase WTe2exhibits both a distinct out-of-plane damping torque (τDL) and exceptional charge–spin interconversion efficiency enabled by strong spin-orbit coupling, positioning it as a prime candidate for spin–orbit torque (SOT) applications in two-dimensional transition metal dichalcogenides. Herein, we report on thickness-dependent unconventional out-of-planeτDLin chemically vapor-deposited (CVD) polycrystalline Td-WTe2(t)/Ni80Fe20/MgO/Ti (Td-WTN-t) heterostructures. Angle-resolved spin-torque ferromagnetic resonance measurements on the Td-WTN-12 structure showed significant spin Hall conductivities ofσSH,y= 4.93 × 103(ℏ/2e) Ω−1m−1andσSH,z= 0.81 × 103(ℏ/2e) Ω−1m−1, highlighting its potential for wafer-scale spin–orbit torque device applications. Additionally, a detailed examination of magnetotransport properties in polycrystalline few-layer Td-WTe2films as a function of thickness revealed a marked amplification of the out-of-plane magnetoresistance, which can be ascribed to the anisotropic nature of charge carrier scattering mechanisms within the material. Spin pumping measurements in Td-WTN-theterostructures further revealed thickness-dependent spin transport properties of Td-WTe2, with damping analysis yielding an out-of-plane spin diffusion length ofλSD≈ 14 nm.
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