Observation of Kondo effect in transition metal dichalcogenides VX 2 (X=Se & Te) due to low-temperature weak ferromagnetism

We report on the electrical transport, magnetotransport, and magnetic properties studies on the transition metal dichalcogenides VSe2 and VTe2 and draw a comprehensive comparison between them. We observe Kondo effect in both systems due to weak ferromagnetic ordering at low temperature , resulting into resistance upturn at 6 K for VSe2 and 12 K for VTe2. From the field dependent resistance measurements we find that the data is fitted best with modified Hamann equation corrected by the quantum Brillouin function for VSe2, while the data is fitted best with modified Hamann equation corrected by the classical Langevin function for VTe2. We attribute the differing formalisms for the same Kondo effect in VSe2 and VTe2 to their extrinsic sample properties rather than the intrinsic nature of the material. Interestingly, we observe a contrasting magnetoresistance (MR) property between these systems across the Kondo temperature. That means, negative MR is found in both systems in the Kondo state. In the normal state MR is positive for VSe2, while it is negligible for VTe2. In addition, both systems show weak ferromagnetism at low temperature due to intercalated V atoms.