Substitutional adsorption mechanism and controllable magnetic properties of Mn on PbTe(1 1 1) surface

Adsorption of Mn adatom on PbTe(1 1 1) surface is investigated by first-principle calculations. A subsurface substitutional adsorption mechanism is found. Mnsingle bondTe bond is stronger and shorter than Pbsingle bondTe bond. This leads to competition. Because of stronger Mnsingle bondTe bond, Mn atoms prefer to be deep into bulk crystal in order to maximum the number of Mnsingle bondTe bond. But the Mnsingle bondTe bonds cannot relax to gain their maximum strength because of the rigidity of the bulk crystal. At the outmost surface layer Mn atoms can relax maximum but the number of Mnsingle bondTe bond is only half of that in bulk. The 2nd layer is the best choice and Mn atoms prefer to form a image pattern, in well agreement with recent experimental work. More importantly, its magnetic state is strain-dependent and this opens a new avenue to fabricate spintronics and spin caloritronics with a high tunneling magnetothermopower based on PbTe.