Fermi Surface Property and Characteristic Crystalline Electric Field Effect in PrIr2Zn20

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We measured the de Haas--van Alphen (dHvA) oscillations, electrical resistivity, magnetic susceptibility, magnetization, and specific heat of PrIr2Zn20, which has recently been suggested as a heavy-fermion superconductor. Several dHvA branches with small frequencies ranging from 0.33\times 10^{6} to 8.00\times 10^{6} Oe were detected in the dHvA experiment, which were well explained by the results of energy band calculations for LaIr2Zn20 using the lattice parameter of PrIr2Zn20. Moreover, the cyclotron effective mass is small, i.e., less than 1m_{0} (m_{0}: rest mass of an electron). This means that 4f electrons are fully localized and do not contribute to the Fermi surface. Similar dHvA results were obtained for the reference compound LuIr2Zn20. Thus, superconductivity in PrIr2Zn20, which has been observed very recently below 0.05 K, is not due to heavy quasiparticles. In fact, the present superconductivity disappears at a magnetic field of 20 Oe. From the experimental results of magnetic susceptibility, magnetization, and specific heat, we estimated the 4f crystalline electric field (CEF) scheme of PrIr2Zn20: \Gamma_{3} (0 K)--\Gamma_{4} (separated from a non-Kramers \Gamma_{3} doublet by 36.0 K)--\Gamma_{1} (86.4 K)--\Gamma_{5} (103 K). On the basis of this CEF scheme, we discuss a broad Schottky peak in the magnetic specific heat at 0.4 K and the metamagnetic-like anomaly of magnetization at H_{\text{m}}\simeq 50 kOe for H\parallel\langle 100\rangle.
2011-07-15

Fermi Surface Property and Characteristic Crystalline Electric Field Effect in PrIr2Zn20

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