Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

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

Han-Jin Noh, En-Jin Cho, Byeong-Gyu Park, Hyowon Park, Ivar Martin, Cristian D. Batista, Pyeongjae Park, Woonghee Cho, Je-Guen Park

TL;DR

This study shows that the magnetic ordering transition in the metallic triangular antiferromagnet Co$_{1/3\pm\epsilon}$TaS$_2$ is driven by small electronic-structure changes. ARPES reveals distinct Fermi-surface topologies for $x\approx 0.325$ (two hexagonal and one circular pockets) and $x\approx 0.340$ (emergent K-pocket) that correlate with nesting between Co $3d$ and Ta $5d$ states, and a 3Q chiral order is favored. DFT+DMFT calculations reproduce key features and show that the most stable ordering vector shifts from $Q=(1/2,0,0)$ to $Q=(1/3,0,0)$ as electron doping and Co$_4$S$_{18}$ tripods modify the band structure and inter-site interactions, indicating correlation effects beyond a simple rigid-band picture. The work demonstrates a localized spin-ordering transition can be induced purely by electronic-structure changes in a metallic magnet, with implications for tuning magnetic states in TLAFs via controlled correlations and nesting.

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$_{1/3\pmε}$TaS$_2$ ($ε\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 $Γ$, 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 DFT+DMFT band structure indicate that the most stable magnetic ordering vector changes to (1/3,0,0) from (1/2,0,0), which is very consistent with the magnetic phase transition around $x$=1/3 in Co$_{x}$TaS$_2$.

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

TL;DR

This study shows that the magnetic ordering transition in the metallic triangular antiferromagnet CoTaS is driven by small electronic-structure changes. ARPES reveals distinct Fermi-surface topologies for (two hexagonal and one circular pockets) and (emergent K-pocket) that correlate with nesting between Co and Ta states, and a 3Q chiral order is favored. DFT+DMFT calculations reproduce key features and show that the most stable ordering vector shifts from to as electron doping and CoS tripods modify the band structure and inter-site interactions, indicating correlation effects beyond a simple rigid-band picture. The work demonstrates a localized spin-ordering transition can be induced purely by electronic-structure changes in a metallic magnet, with implications for tuning magnetic states in TLAFs via controlled correlations and nesting.

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 CoTaS (0.007) is induced by the electronic structure change in the system. The ARPES-measured Fermi surface (FS) maps of CoTaS show two hexagonal and one circular hole-like FSs around , which matches well with the triple-\textbf{Q} state by taking into account the contribution of nesting vectors occurring between Co 3 and Ta 5 orbitals. In the case of CoTaS, a new electron pocket around K appears and the FS geometry changes as a result of the correlation effect of CoS tripods forming in the system. The magnetic susceptibility calculations based on the DFT+DMFT band structure indicate that the most stable magnetic ordering vector changes to (1/3,0,0) from (1/2,0,0), which is very consistent with the magnetic phase transition around =1/3 in CoTaS.

Paper Structure

This paper contains 3 sections, 2 equations, 5 figures.

Table of Contents

  1. Experimental Details
  2. Calculational Methods
  3. Acknowledgments

Figures (5)

  • Figure 1: Crystal structure and magnetic phase diagram of Co$_x$TaS$_2$ (a) The unit cell of Co$_{1/3}$TaS$_2$. (b) Composition-dependent magnetic phase diagram for Co$_{x}$TaS$_2$ (0.3 $< x <$ 0.34). PPark_PRB The mark X denotes the Co composition in this work. (c) A Co$_4$S$_{18}$ tripod in a van der Waals gap of over-doped Co$_{x}$TaS$_2$.
  • Figure 2: ARPES-measured electronic structure of Co$_{0.325}$TaS$_2$(a) Measured FS map obtained with 90 eV photons. (a1, a2) The energy dispersion images with the Wannier function based DFT calculations along the dotted line a$_1$ and a$_2$ in (a). (b) FS map obtained with 50 eV photons in $s$-polarization mode. (b1) The energy dispersion image along the dotted line b$_1$ in (b). (c) Schematic FS based on (a) and (b). (d) FS map obtained with 60 eV photons. (d1) The energy dispersion image along the dotted line d$_1$ in (d).
  • Figure 3: ARPES-measured electronic structure of Co$_{0.340}$TaS$_2$. (a) Measured FS obtained with 90 eV photons. (a1, a2) The energy dispersion image along the dotted line a$_1$ and a$_2$ in (a). (b) FS obtained with 50 eV photons. (b1, b2) The energy dispersion image along the dotted line b$_1$ and b$_2$ in (b). (c) Schematic FS based on (a) and (b). (d) FS obtained with 70 eV photons.
  • Figure 4: Schematic energy diagrams for Co$_4$S$_{18}$ tripod (a) Energy level splitting of Co 3$d$ orbitals under a crystal electric field of D$_{3h}$ symmetry. (b) Schematic electron configuration for Co 3$d$-3$d$ direct bonding in a tripod. (c) A part of Co$_4$S$_{18}$ tripod. Edge sharing of CoS$_6$ octahedra enables not only the Co-Co direct bonding but also Co-S-Co super-exchange interaction.
  • Figure 5: DMFT calculations for UD-CTS and OD-CTS (a) The DMFT band structure for UD-CTS. The green lines are the DFT bands. (b) The DMFT FS for UD-CTS. (c) The magnetic susceptibility for UD-CTS. (d-f) The same calculations to (a-c) for OD-CTS. (g) The doping dependence of the polarizability $\chi^{0}(q,\omega=0)$.