Near-room-temperature ferromagnetic 1T Nb1−xCrxTe2 from doping-induced phase transition of 1T’ NbTe2

Magnetic transition metal dichalcogenides exhibit unique spintronic properties, making them highly promising for advanced spintronic devices. It is unpreparable 1T NbTe₂, rather than the stable 1T’ phase, that has been theoretically predicted to host nontrivial topology, but its thermodynamic structural instability hinders its development in spintronic applications. Heteroatom doping is effective in not only stabilizing the 1T phase but also introducing magnetism. Herein, we synthesized a series of Nb_1−xCr_xTe₂ (x = 0, 0.1, 0.2, 1/3, 0.4) crystals and discovered the 1T Nb_2/3Cr_1/3Te₂ phase for the first time. Observed 1T’-to-1T structural transition occurs in NbTe₂ due to the Cr doping. Thermodynamically stable Nb_2/3Cr_1/3Te₂ is confirmed to be a 1T phase from density functional theory calculations. A notable transition from diamagnetic to ferromagnetism was found in Nb_1−xCr_x-Te₂ with the ratio of Cr increasing. The magnetism of 1T Nb_2/3Cr_1/3Te₂ primarily originates from localized Cr 3d electrons. This crystal achieves a Curie temperature of 254 K, surpassing most Cr-based van der Waals ferromagnets. Furthermore, 1T Nb_2/3Cr_1/3Te₂ displays metallic behavior coexisting with the Kondo effect and a robust positive magnetoresistance (32.1% at 2 K, μ₀H = 9 T). This work unveils a doping-induced phase transition mechanism and provides new layered ferromagnetic materials for spintronic devices.