Exchange interaction and its tuning in magnetic binary chalcogenides

Abstract

Using a first-principles Green's function approach we study magnetic properties of the magnetic binary tetradymite chalcogenides Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 . The magnetic coupling between transition-metal impurities is long range, extends beyond a quintuple layer, and decreases with increasing number of d electrons per 3d atom. We find two main mechanisms for the magnetic interaction in these materials: the indirect exchange interaction mediated by free carriers and the indirect interaction between magnetic moments via chalcogen atoms. The calculated Curie temperatures of these systems are in good agreement with available experimental data. Our results provide deep insight into exchange interactions in magnetic binary tetradymite chalcogenides and open a way to design new materials for promising applications.

Signatures of Dirac fermion-mediated magnetic order

“…A detailed theoretical modelling of our experimental findings goes beyond the scope of the present work since it requires a detailed knowledge of the exchange interaction and the constant energy contours. Indeed, it has been recently shown that the effective exchange interaction among single magnetic impurities is reduced by increasing the number of electrons per atom 37 . Furthermore, we would like to point out that the evolution from a circle to a convex hexagon may strongly affect the behaviour of topological state in the presence of magnetic impurities since it can strongly enhance the strength of the RKKY interaction along some direction as described in ref.…”

Electronic and transport properties of the Mn-doped topological insulatorBi2Te3: A first-principles study

“…1 It has led to ferromagnets with low Curie temperatures below 20 K. [9][10][11][12] Theoretical calculations, 13 however, obtain a monotonic increase of the Curie temperature with increasing doping. Doping by transition metal impurities leads to formation of carriers, e.g., Mn-impurities in Bi 2 Te 3 which substitute Bi-atoms will act as acceptors.…”

Impurity states in the magnetic topological insulator V:(Bi,Sb)2Te3

“…Recently, Vergniory et al 11 have shown that the magnetism picture in these systems may be more complex than the Van-Vleck mechanism so far discussed 2,7,8,13 . Their calculations showed that the exchange constants (magnitude and sign) strongly depend on the filling of the d-states, and that competing coupling mechanisms may simultaneously take place.…”

“…First-principles calculations have predicted a metallic impurity band at the Fermi level (E F ) for different V-doped TIs, yet a fully gapped band structure for Cr-doped systems 2,10,11,16 .…”