Static and Dynamic Electronic Properties and the Possible Magnetic Structure of the $4f^3$-${\mathrm{\Gamma }}_6$ System NdCo2Zn${}_{18}$Ga${}_2$ Investigated Using ${}^{59}$Co Nuclear Quadrupole Resonance

We report ${}^{59}$Co nuclear quadrupole resonance (NQR) measurements on the Nd-based compound NdCo${}_2$Zn${}_{18}$Ga${}_2$, which undergoes an antiferromagnetic transition at $T_{\mathrm{N}}=1.5$ K. Although the NQR spectra show no detectable change across $T_{\mathrm{N}}$, the nuclear spin-lattice relaxation rate, $1\mathrm{/}{T}_1$, exhibits a clear anomaly at $T_{\mathrm{N}}$. An analysis based on the alignment of the Nd moments demonstrates that the internal magnetic fields generated by these moments cancel each other at the Co sites. If the nearest-neighbor Nd moments align antiferromagnetically, this finding suggests that Ga substitution removes magnetic frustration, thereby increasing $T_{\mathrm{N}}$.