Bulk properties of the chiral metallic triangular antiferromagnets Ni1/3NbS2 and Ni1/3TaS2

T M1/3MS2 (TM = 3d transition metal, M = Nb, Ta) has recently attracted increasing attention due to its wide variety of fascinating magnetic structures and the chiral arrangement of intercalated TM atoms. We investigated the bulk properties of Ni1/3NbS2 and Ni1/3TaS2 using magnetization, transport, heat capacity, powder neutron diffraction, and x-ray absorption spectroscopy. Ni1/3NbS2 undergoes a phase transition at 84 K, developing an antiferromagnetic helical order with a very long period along the c axis (33c). On the other hand, a simple A-type spin configuration was observed for Ni1/3TaS2 below 158 K, where the spins are aligned to the c axis. These magnetic structures, combined with lattice chirality and metallicity, can lead to various intriguing transport properties, making Ni1/3NbS2 and Ni1/3TaS2 promising material candidates for future studies on antiferromagnetic spintronics.