Electrical and Magnetic Properties of a Single Crystal UCu₂Si₂

Abstract

We have succeeded in growing a high-quality single crystal of UCu 2 Si 2 with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu 2 Si 2 is found to order antiferromagnetically below T N =106 K, and follows a successive ferromagnetic ordering at T C =100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ( c -axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction ( a -axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes into a ferromagnetic magnetization curve below T C =100 K. The saturation moment is determined as 1.75 µ B /U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/(K 2 ·mol).