Half-metallicity, magnetism and electrical resistivity of Sn1−xMnxTe alloys in rock salt and zinc blende structures

• We study electronic structure and magnetic properties of Mn-doped semiconductor SnTe.
• We find one antiferromagnetic half-metallic case: Sn3Mn1Te4 in rock salt structure.
• We show that the presence of ‘holes’ may turn antiferromagnetic Mn–Mn interactions to ferromagnetic.
• Results are compared with available experimental data.

This work presents the results for the magnetic properties of the compound SnTe doped with 3d transition metal Mn from the viewpoint of potential application in spintronics. We report a systematic density-functional study of the electronic structure and magnetic properties of these ternary compounds in both rock salt and zinc blende structures. In both cases, it is the Sn-sublattice that is doped with Mn. Among the various compounds studied, we identify one as a possible half-metallic candidate: 25% Mn-doping of the Sn-sublattice in the rock salt structure. Others are either magnetic semiconductors or metals. Exchange interaction between the Mn atoms is discussed and results for resistivities for various compositions in the two structures are compared. For low Mn concentration, the zero temperature ground state of the compound is found to be semiconducting and the Mn–Mn exchange interactions are dominantly antiferromagnetic. The weakly ferromagnetic interaction and ordering found in experiments is shown to be ‘carrier induced’. It is shown that ferromagnetic interactions between the Mn atoms are caused by the presence of ‘holes’. Another likely cause is the presence of extra Te atoms in interstitial locations, which seems to suppress Mn–Mn antiferromagnetic interactions. This is supported by the earlier experimental observation that a weak ferromagnetism occurs in these alloys for low Mn concentration only if the samples are subjected to additional Te-flux.