Site-specific $^{13}$C NMR study on locally distorted triangular lattice of organic conductor $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$

TL;DR

This study uses site-specific $^{13}$C NMR and other measurements to investigate whether geometrical frustration or disorder influences the magnetic properties of a quasi-two-dimensional organic conductor with a distorted triangular lattice.

Contribution

It demonstrates that magnetic properties are unaffected by lattice distortion and are more likely due to disorder, challenging the assumption that frustration dominates magnetism in this system.

Findings

Magnetic characteristics are similar in pure and substituted samples.

Magnetic properties at substituted sites match those in the bulk.

Disorder, not geometrical frustration, likely influences magnetic behavior.

Abstract

To verify the effect of geometrical frustration, we artificially distort the triangular lattice of quasi-two-dimensional organic conductor $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ [BEDT-TTF: bis(ethylenedithio)terathiofulvalene] by analogous-molecular substitution and apply $^{13}$C NMR of bulk and substituted sites, electric conductivity, and static magnetic susceptibility measurements. The results indicate that the magnetic characteristics of the substituted sample are quantitatively similar to those of the pure sample. Moreover the magnetic characteristics at the substituted sites are also the same as in the bulk. These results suggest that the observed magnetic properties may not be due to the geometrical frustration but the importance of disorder.