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

$T{M}_{1/3}M{S}_{2}$ ($TM=3d$ transition metal, $M=\mathrm{Nb},\phantom{\rule{0.16em}{0ex}}\mathrm{Ta}$) has recently attracted increasing attention due to its wide variety of fascinating magnetic structures and the chiral arrangement of intercalated $\mathit{TM}$ atoms. We investigated the bulk properties of ${\mathrm{Ni}}_{1/3}\mathrm{Nb}{\mathrm{S}}_{2}$ and ${\mathrm{Ni}}_{1/3}\mathrm{Ta}{\mathrm{S}}_{2}$ using magnetization, transport, heat capacity, powder neutron diffraction, and x-ray absorption spectroscopy. ${\mathrm{Ni}}_{1/3}\mathrm{Nb}{\mathrm{S}}_{2}$ 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 ${\mathrm{Ni}}_{1/3}\mathrm{Ta}{\mathrm{S}}_{2}$ 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 ${\mathrm{Ni}}_{1/3}\mathrm{Nb}{\mathrm{S}}_{2}$ and ${\mathrm{Ni}}_{1/3}\mathrm{Ta}{\mathrm{S}}_{2}$ promising material candidates for future studies on antiferromagnetic spintronics.