Magnetic ordering and superconductivity in the R2Ir3Ge5(R=Y,La,Ce–Nd,Gd–Tm,Lu) system

Abstract

We report crystal structure, electrical resistivity, magnetic susceptibility, isothermal magnetization, and heat-capacity studies on polycrystalline samples of the intermetallic series R2Ir3Ge5 (R=Y, La, Ce–Nd, Gd–Tm, Lu) from 1.5 to 300 K. We find that the compounds for R=Y, La-Dy, crystallize in the tetragonal Ibam (U2Co3Si5 type) structure whereas the compounds for R=Er–Lu, crystallize in a different orthorhombic structure with a space group Pmmn. Samples of Ho2Ir3Ge5 were always found to be multiphase. The compounds for R=Y–Dy which adopt the Ibam type structure show a metallic resistivity with a tendency of saturation at high temperatures whereas the compounds with R=Er, Tm, and Lu show an anomalous behavior in the resistivity with a semiconducting increase in ρ as we go down in temperature from 300 K. Interestingly we had earlier found a positive temperature coefficient of resistivity for the Yb sample in the same temperature range. We will compare this behavior with similar observations in the compounds R3Ru4Ge13 and RBiPt. La2Ir3Ge5 and Y2Ir3Ge5 show bulk superconductivity below 1.8 K and 2.5 K, respectively. Our results confirm that Ce2Ir3Ge5 shows a Kondo-lattice behavior and undergoes antiferromagnetic ordering below 8.5 K. Most of the other compounds containing magnetic rare-earth elements undergo a single antiferromagnetic transition at low temperatures (T<~12K) while Gd2Ir3Ge5, Dy2Ir3Ge5, and Nd2Ir3Ge5 show multiple transitions. The TN’s for most of the compounds roughly scale with the de Gennes factor, which suggests that the primary mechanism of interaction leading to the magnetic ordering of the magnetic moments may be the Ruderman-Kittel-Kasuya-Yosida interaction. The ordering temperature of 8.5 K for Ce2Ir3Ge5 is anomalously large compared to the TN for Gd2Ir3Ge5 which is about 12 K. There are signs of strong CEF influence on the measured properties for the series.

Source-reported materials — not catalogue approval

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