Electrical resistivity ρ specific heat C, magnetization M measurements are reported on four compounds, LaRu2Zn20, PrRu 2Zn20, LaIr2Zn20, and PrIr2Zn20, which crystallize in a cubic CeCr2Al20- type structure. LaRu2Zn20, LaIr2Zn20, and PrIr2Zn20 show superconducting transitions at TC = 0:2, 0.6, and ∼0:05 K, respectively, whereas PrRu 2Zn20 remains a normal state down to 0.04 K. This is the first observation of superconductivity in the family of RT2X 20 (T = transition metal; X = Al and Zn). Furthermore, structural phase transitions manifest themselves at Ts = 150, 138, and 200K for LaRu2Zn20, PrRu2Zn20, and LaIr 2Zn20, respectively. No magnetic transition is found in PrRu2Zn20 and PrIr2Zn20 down to 1.8 K. On cooling PrIr2Zn20 below 2K, the specific heat divided by temperature, C=T, continuously increases and reaches 5 J/(K 2 •mol) at 0.4 K, suggesting that Pr 4f2 electrons are involved in the heavy-fermion state, as observed in a related compound YbCo2Zn20.
ASJC Scopus subject areas
- Physics and Astronomy(all)