Magnetism and superconductivity in M₅Rh₄Ge₁₀ (M=Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y)

Abstract

Low-temperature resistivity, magnetization and heat-capacity studies are reported for the isostructural M₅Rh₄Ge₁₀ (M=Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y) series. Some of the compounds (M=Gd, Tb, Er, and Tm) show multiple magnetic transitions below 15 K while others (M=Dy and Ho) exhibit only a single magnetic transition. The four magnetic transitions observed for Gd₅Rh₄Ge₁₀ and Tb₅Rh₄Ge₁₀ are unusual in that the one at the highest temperature is a second-order phase transition while the other three are first-order transitions probably involving moment reorientations. An anisotropic exchange interaction is proposed as the cause of the multiple transitions. Of the nonmagnetic compounds, Lu₅Rh₄Ge₁₀ shows superconductivity below 2.4 K whereas Y₅Rh₄Ge₁₀ remains normal down to 1.7 K. The results are compared with those of the previously investigated M₅Ir₄Si₁₀ series.