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) MX2 (M = Ti to Mn, and X = S to Te) atomic chains is proposed. The results reveal that the MX2 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 TiX2 atomic chains are nonmagnetic semiconductors, while the VX2, CrX2, and MnX2 chains are unipolar magnetic, bipolar magnetic, and antiferromagnetic semiconductors, respectively. In addition, the VX2, CrX2, and MnX2 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 MnX2 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 MX2 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 MX2 chains implies that armchair (7,7) or armchair (8,8) carbon nanotubes are appropriate sheaths for growing MX2 atomic single-chains in a confined channel. This study reveals the diverse magnetic properties of MX2 atomic single-chains and provides a promising building block for nanoscale electronic and spintronic devices.