Field-tuned critical fluctuations in YFe${}_2$Al${}_{10}$: Evidence from magnetization, ${}^{27}$Al NMR, and NQR investigations

We report magnetization, specific heat, and NMR investigations on YFe${}_2$Al${}_{10}$ over a wide range of temperature and magnetic field and zero field (NQR) measurements. Magnetic susceptibility, specific heat, and spin-lattice relaxation rate divided by $T(1/T_{1}T)$ follow a weak power law ($\sim$$T^{-0.4}$) temperature dependence, which is a signature of the critical fluctuations of Fe moments. The value of the Sommerfeld-Wilson ratio and the linear relation between $1/T_{1}T$ and $\chi$ suggest the existence of ferromagnetic correlations in this system. No magnetic ordering down to 50 mK in $C_p\left(T\right)/T$ and the unusual $T$ and $H$ scaling of the bulk and NMR data are associated with a magnetic instability which drives the system to quantum criticality. The magnetic properties of the system are tuned by field wherein ferromagnetic fluctuations are suppressed and a crossover from quantum critical to Fermi-liquid behavior is observed with increasing magnetic field.

Figure 1

(a) The temperature dependence of $\chi \left(T\right)$ in different magnetic fields. The solid line displays the $T^{-0.5}$ behavior. (b) The $T$ dependence of $1/\chi \left(T\right)$ with a Curie-Weiss fit. (c) Arrott plot of the magnetization. The inset show $M$ vs $H$ at 2 K with a fit to $H^{0.45}$.

Figure 2

(a) Field sweep NMR PC and SC spectra ($H\perp b$) with a simulation at 80 MHz. The inset shows the NQR spectra ($\pm 3/2⟺;\pm 5/2$) on a PC sample at different $T$.

Figure 3

(a) The $T$ dependence of $1/T_{1}T$ in various magnetic fields. The solid line is a fit to $T^{-0.4}$ ($1/T_{1}T$ values are shifted for better clarity). (b) The linear relation between $1/T_{1}T$ and $\chi$ with $T$ as an implicit parameter.

Figure 4

Temperature dependence of $C_p/T$. The solid line is a fit to $T^{-0.35}$. (b) Field dependence of $1/T_1$ at 2 K with a fit as discussed in the text. (c) $1/T_{1}T$ vs $T$ at 0.545 and 7.27 T.