Comparative study of Kondo effect in Vanadium dichalcogenides VX2 (X=Se & Te)

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 induced by the exchange interaction between localized moments and conduction electrons at low temperature, resulting into resistance upturn at 6 K for VSe2 and 17 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. 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.