Magnetic properties of the heavy-fermion antiferromagnet CeMg${}_3$

We have grown the single crystals of CeMg${}_3$ and its nonmagnetic analog LaMg${}_3$, which crystallize in the cubic crystal structure with the space group $\mathit{Fm}$$\overline{3}m$, and studied their magnetic properties on well-oriented single crystals by measuring the magnetic susceptibility, magnetization, electrical resistivity, and heat capacity. CeMg${}_3$ orders antiferromagnetically with a Néel temperature $T_{\mathrm{N}}$ of 2.6 K. The specific heat capacity at low temperature exhibits an enhanced Sommerfeld coefficient of 370 mJ/K${}^2$ mol, indicating the heavy-fermion nature of CeMg${}_3$. An estimation of the Kondo temperature $T_{\mathrm{K}}$ was made and it was found that it is of a magnitude similar to that of $T_{\mathrm{N}}$. The reduced value of the magnetization below the ordering temperature, together with the reduced entropy at the magnetic ordering temperature and the enhanced low-temperature heat capacity, indicates that Kondo effect plays a significant role in this compound. The electrical resistivity measurement suggests that CeMg${}_3$ is a Kondo lattice compound. We have performed a crystalline electric field (CEF) analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is a ${\Gamma }_7$ doublet with an overall splitting of 191 K.

Figure 1

A representative powder x-ray diffraction pattern of CeMg${}_3$.

Figure 2

(a) Temperature dependence of magnetic susceptibility of CeMg${}_3$ for field parallel to [100]. The inset shows the low-temperature part of the magnetic susceptibility in an expanded scale. (b) Inverse magnetic susceptibility of CeMg${}_3$. The solid line is a fit to Curie-Weiss law.

Figure 3

Isothermal magnetization of CeMg${}_3$ for $H\parallel$ [100] at T $=$ 1.8 K measured in a vibrating sample magnetometer.

Figure 4

Temperature dependence of electrical resistivity $\rho (T)$ of CeMg${}_3$ and LaMg${}_3$ in the temperature range 1.9 to 300 K. The inset shows the magnetic part of the electrical resistivity ${\rho }_{\mathrm{mag}}(T)$.

Figure 5

(a) Temperature dependence of the specific heat capacity in CeMg${}_3$ and LaMg${}_3$. The top insets show the low-temperature plots of $C$ vs $T$ and $C/T$ vs $T$ of CeMg${}_3$. The bottom inset shows the $C/T$ vs $T^2$ plot. (b) $C_{\mathrm{mag}}$/$T$ vs $T$ of CeMg${}_3$. The calculated entropy is plotted on the right axis.

Figure 6

(a) $C/T$ versus $T$ plot of CeMg${}_3$ in applied magnetic fields, in the temperature range 0.5 to 4 K. The inset shows the low-temperature part of the $C/T$ versus $T^2$ plot.

Figure 7

Estimation of the Kondo temperature from the jump in the magnetic part of the heat capacity. The solid line is the plot of Eq. (1). See text for details.

Figure 8

(a) Magnetic part of the specific heat capacity of CeMg${}_3$. The solid line is the calculated Schottky heat capacity, which gives an energy separation of 191 K between the ground state doublet and the excited quartet. (b) Inverse magnetic susceptibility of CeMg${}_3$. The solid line is based on the CEF calculation.