Easy-Axis Kagome Antiferromagnet: Local-Probe Study of ${\mathrm{Nd}}_3{\mathrm{Ga}}_5{\mathrm{SiO}}_{14}$

We report a local-probe investigation of the magnetically anisotropic kagome compound ${\mathrm{Nd}}_3{\mathrm{Ga}}_5{\mathrm{SiO}}_{14}$. Our zero-field muon spin relaxation ($\mu \mathrm{SR}$) results provide direct evidence of a fluctuating collective paramagnetic state down to 60 mK, supported by a wipeout of the Ga nuclear magnetic resonance (NMR) signal below 25 K. At 60 mK a dynamics crossover to a much more static state is observed by $\mu \mathrm{SR}$ in magnetic fields above 0.5 T. Accordingly, the NMR signal is recovered at low $T$ above a threshold field, revealing a rapid temperature and field variation of the magnetic fluctuations.

Figure 1

${}^{69,71}\mathrm{Ga}$ NMR spectra of NGS at 46.01 MHz and $\mathbf{H}\Vert \mathbf{c}$. The 1.2 K spectrum is translated vertically. Arrows indicate the satellite (S) lines at 80 K. The inset (a) highlights central (C) peaks of the three crystallographically nonequivalent Ga sites at 80 K; the vertical dashed line corresponds to a reference field. The inset (b) shows the network of ${\mathrm{Nd}}^{3+}$ magnetic moments and the location of the in-plane Ga(1) sites and Ga(2, 3) sites separating kagome planes.

Figure 2

Scaling of the ${}^{71}\mathrm{Ga}$ NMR shift with bulk susceptibility. Inset: The susceptibility crossover at 1 T.

Figure 3

(a) Zero-field (ZF) muon spin relaxation rate $\lambda$ and ${}^{71}\mathrm{C}(3)$ NMR spin-lattice relaxation rate $1/T_1$ measured at 46.01 MHz (3.55 T) and $\mathbf{H}\Vert \mathbf{c}$. Inset: ZF relaxation of muon polarization. (b) Wipeout of the NMR intensity. The high-$T$ (low-$T$) data were taken at 46.01 MHz (29.61 MHz) at different fields. Dashed lines are a guide to the eyes. Inset: absence of the NQR echo at 1.2 K and 15 MHz.

Figure 4

Field dependence of the muon relaxation rate $\lambda$ at 60 mK and the ${}^{69}\mathrm{Ga}$ NMR $1/T_1$ at 1.2 K on several C and S lines. The solid line gives the predicted $H$ dependence of $\lambda$ in the dynamical case [Eq. (1)]. Inset: relaxation of muon polarization in various LF fields at 60 mK.