Experimental confirmation of the magnetic ordering transition induced by an electronic structure change in the metallic triangular antiferromagnet Co${}_{1/3}$TaS${}_2$

Abstract

We report ARPES studies combined with DFT+DMFT calculations to confirm that the magnetic ordering vector transition from \textbf{Q}=(1/2,0,0) to \textbf{Q}=(1/3,0,0) in the metallic triangular antiferromagnets Co${}_{1/3\pm \hat{I}\mu }$TaS${}_2$ ($\hat{I}\mu \approx$0.007) is induced by the electronic structure change in the system. The ARPES-measured Fermi surface (FS) maps of Co${}_{0.325}$TaS${}_2$ show two hexagonal and one circular hole-like FSs around $\hat{I}“$, which matches well with the triple-\textbf{Q} state by taking into account the contribution of nesting vectors occurring between Co 3$d$ and Ta 5$d$ orbitals. In the case of Co${}_{0.340}$TaS${}_2$, a new electron pocket around K appears and the FS geometry changes as a result of the correlation effect of Co${}_4$S${}_{18}$ tripods forming in the system. The magnetic susceptibility calculations based on the charge-self-consistent DFT+DMFT band structures and the random phase approximation indicate that the most stable magnetic ordering vector (1/2,0,0) split into (1/6,0,0) and (1/2,0,0), which is consistent with the magnetic phase transition around $x$=1/3 in Co${}_x$TaS${}_2$.

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