Magnetism in 2D TMDC

Abstract

This chapter discussesmagnetism in few-layer transitionmetal dichalcogenides associated with the presence of edges, defects, dislocations and grain boundaries as well as dopants. Defect-free pristine TMDCs are nonmagnetic because there are no unsaturated bonds and no magnetic elements. In [1] it was additionally noted that 2H-MoS2 is macroscopically nonmagnetic, because the Mo4+ ions are in a trigonal prismatic local coordination in which the two 4d electrons are spin-antiparallel and the net magnetic moment is zero, although it is not clear to what extent this is significant. At the same time, in real materials there are always edges, dislocations, grain boundaries and other imperfections that may have an effect on magnetic properties. One of the first reports of magnetism in TMDC was [2], where ferromagnetism (FM) was observed in polycrystalline MoS2 films (Fig. 10.1), while it was not observed in single crystals,1 which was attributed to the presence of imperfections, such as grain boundaries. In addition, magnetism may be induced by doping with magnetic elements. Finally, in TMDC there exists a specific possibility of controlling magnetism by application of strain. These issues form the subject of the present chapter.