Crystal structure and anisotropic magnetic properties of new ferromagnetic Kondo lattice compound Ce(Cu,Al,Si)2

Abstract Single crystals of the new compound CeCu 0.18 Al 0.24 Si 1.58 have been grown by high-temperature solution growth method using a eutectic Al-Si mixture as flux. This compound is derived from the binary CeSi 2 (tetragonal α-ThSi 2 -type, Pearson symbol tI 12, space group I 4 1 /amd ) obtained by partial substitution of Si by Cu and Al atoms but showing full occupation of the Si crystal site (8 e ). While CeSi 2 is a well-known valence-fluctuating paramagnetic compound, the CeCu 0.18 Al 0.24 Si 1.58 phase orders ferromagnetically at T C =9.3 K. At low temperatures the easy-axis of magnetization is along the a- axis, which re-orients itself along the c -axis above 30 K. The presence of hysteresis in the magnetization curve, negative temperature coefficient of resistivity at high temperatures, reduced jump in the heat capacity and a relatively lower entropy released up to the ordering temperature, and enhanced Sommerfeld coefficient (≈100 mJ/mol K 2 ) show that CeCu 0.18 Al 0.24 Si 1.58 is a Kondo lattice ferromagnetic, moderate heavy fermion compound. Analysis of the high temperature heat capacity data in the paramagnetic region lets us infer that the crystal electric field split doublet levels are located at 178 and 357 K, respectively, and Kondo temperature (8.4 K) is of the order of T C in CeCu 0.18 Al 0.24 Si 1.58 .