Low-temperature physical properties of a new cubic compound CeMgZn$_2$

CeMgZn$_2$ crystallizes in a Heusler-type cubic structure (space group $Fm\overline{3}m$, $O_h^{\rm{5}}$, No. 225) [1]. No physical properties of this compound have been reported thus far. Since the Ce ions on a face-centered cubic lattice form a network of edge-sharing tetrahedra, geometrical frustration may affect the physical properties of this compound. In this study, polycrystalline samples of CeMgZn$_2$ have been grown and their magnetic and transport properties have been examined by measuring the magnetic susceptibility, the electrical resistivity, and the specific heat. The effective magnetic moment ${\mu}_{\rm{eff}}$ and the paramagnetic Curie temperature ${\theta}_{\rm{P}}$ have been determined to be 2.75 ${\mu}_{\rm{B}}$/Ce and -73 K, respectively, which implies that the Ce ions are trivalent and the magnetic interaction between Ce moments is antiferromagnetic. The magnetic susceptibility measured at 0.1 T shows a shoulder and a cusp at $T_{\rm{N1}}$ = 5.4 K and $T_{\rm{N2}}$ = 3.1 K, respectively. $T_{\rm{N1}}$ and $T_{\rm{N2}}$ correspond to the antiferromagnetic-transition temperatures since these temperatures decrease with increasing magnetic field. In contrast to the clear anomaly at $T_{\rm{N2}}$ in the susceptibility, no anomalies appear at $T_{\rm{N2}}$ in the specific heat (see Fig. 1). Note that $|{\theta}_{\rm{P}}|/T_{\rm{N1}}$ = 13.5 is comparable to that of CePdAl ($|{\theta}_{\rm{P}}|/T_{\rm{N}}$ = 12.6) whose magnetic state is inferred to be affected by geometrical frustration [2]. From the results of magnetic susceptibility and magnetization measurements, the magnetic field vs. temperature phase diagram has been constructed (see Fig. 2). Below 3 T, we have found at least four magnetic phases. The geometrical frustration may be responsible for the appearance of many magnetic phases.

[1] V. Pavlyuk, P. Solokha, G. Dmytriv, B. Marciniak, and V. Paul-Boncour, Acta. Cryst., E63, i161 (2007).
[2] A. D$\rm{\ddot{o}}$nni, G. Ehlers, H. Maletta, P. Fischer, H. Kitazawa, and M. Zolliker, J. Phys. Condens. Matter, 8, 11213 (1996).

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