Effect of Ge substitution on the magnetic ordering of URu₂Si₂

Abstract

Single phase alloys of composition URu₂Si_2−xGe_x for 0 ≤ x ≤ 0.6 crystallising in the ThCr₂Si₂ type structure have been prepared. The lattice volume increases with increasing Ge content. For x > 0.6, X-ray diffraction patterns show the presence of impurity phases along with the ThCr₂Si₂-type phase. The magnetic susceptibility of the alloys is practically the same for all the alloys down to 77K. Heat capacity measurements in the range 2 to 25 K show that the magnetic ordering temperature T_N is lowered with Ge substitution. A comparison of these results with the effect of external pressure on T_N and with La substituted alloys indicates that the decrease of T_N is due to the negative lattice (chemical) pressure induced by Ge substitution.