Near-Room-Temperature Ferromagnetic 1T Nb1−xCrxTe2 from Doping-Induced Phase Transition of 1T′ NbTe2
Magnetic transition metal dichalcogenides (TMDs) offer intrinsic spin polarization for spintronic devices, yet ferromagnetic TMDs remain scarce. The theoretically predicted nontrivial topological 1T NbTe2 is thermodynamically unstable relative to the 1T′ phase under ambient conditions, impeding its spintronic application. Heteroatom doping can stabilize the 1T phase and introduce magnetism. We synthesized Nb1−xCrxTe2 (x = 0, 0.1, 0.2, 1/3, 0.4) crystals and discovered the 1T Nb2/3Cr1/3Te2 phase. Cr doping induces a 1T′-to-1T structural transition in NbTe2. Density functional theory confirms the thermodynamic stability of 1T Nb2/3Cr1/3Te2. Magnetic measurements reveal a transition from diamagnetic to ferromagnetic behavior with increasing Cr content. The ferromagnetism in 1T Nb2/3Cr1/3Te2 originates primarily from localized Cr 3d electrons, achieving a Curie temperature (TC) of 254 K, surpassing most Cr-based van der Waals ferromagnets. The compound exhibits metallic behavior coexisting with the Kondo effect and a positive magnetoresistance of 32.1% at 2 K under μ0H = 9 T. This work unveils a doping-induced phase transition mechanism and provides a new layered ferromagnetic material for spintronic devices.