Single crystal growth of RNiX2 (R=U and Ce, X=Si and Ge) ternary compounds

We have attempted to grow single crystal of RNiX2 (R=U and Ce, X=Si and Ge) which crystallizes in orthorhombic CeNiSi2-type layered structure. Although RNiX2 compounds do not melt congruently, CeNiGe2 and UNiSi2 single crystals can be grown by the Czochralsky method from Ge- or Si- rich sample as the initial one. As for CeNiGe2, the nominal composition of each compounds are refined to be CeNixGe2 (x < 1) from the result of SEM analysis. Although it is well-known that CeNiGe2 orders antiferromagnetically at T-N1 = 3.8 K and T-N2 = 3.2 K, both T-N1 and T-N2 depend on the concentration of Ni. It may comes from the fact that the magnetic property relies on a structural homogeneity and a stoichiometry. UNiSi2, which orders ferromagnetically at T-C = 95 K, displays the anisotropic behavior of the magnetization. The easy magnetization direction is in the ac plane. From the result of the magnetic susceptibility along the ac plane, the effective magnetic moment is obtained to be mu(eff) similar to 2.47 mu B, which is larger than that of porycrystalline sample, mu(eff) similar to 1.9 mu B.