Transition metal dichalcogenide magnetic atomic chains.

Reducing the dimensions of a material to the atomic scale endows them with novel properties that are significantly different from their bulk counterparts. A family of stoichiometric transition metal dichalcogenide (TMD) MX 2 (M = Ti to Mn, and X = S to Te) atomic chains is proposed. The results reveal that the MX 2 atomic chains, the smallest possible nanostructure of a TMD, are lattice-dynamically stable, as confirmed from their phonon spectra and ab initio molecular dynamics simulations. In contrast to their bulk and two-dimensional (2D) counterparts, the TiX 2 atomic chains are nonmagnetic semiconductors, while the VX 2 , CrX 2 , and MnX 2 chains are unipolar magnetic, bipolar magnetic, and antiferromagnetic semiconductors, respectively. In addition, the VX 2 , CrX 2 , and MnX 2 chains can be converted via carrier doping from magnetic semiconductors to half metals with reversible spin-polarization orientation at the Fermi level. Of these chains, the MnX 2 chains exhibit either ferromagnetic or antiferromagnetic half metallicity depending on the injected carrier type and concentration. The diverse and tunable electronic and magnetic properties in the MX 2 chains originate, based on crystal field theory, from the occupation of the metal d orbitals and the exchange interaction between the tetrahedrally coordinated metal atoms in the atomic chain. The calculated interaction between the carbon nanotubes and the MX 2 chains implies that armchair (7,7) or armchair (8,8) carbon nanotubes are appropriate sheaths for growing MX 2 atomic single-chains in a confined channel. This study reveals the diverse magnetic properties of MX 2 atomic single-chains and provides a promising building block for nanoscale electronic and spintronic devices.