Magnetic and Superconducting Properties of LaIrSi₃ and CeIrSi₃ with the Non-centrosymmetric Crystal Structure

Abstract

Single crystals of LaIrSi 3 and CeIrSi 3 were grown by the Czochralski pulling method in a tetra-arc furnace and the magnetic and superconducting properties, together with superconductivity in CeIr 1- x Co x Si 3 , were clarified by measuring the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas–van Alphen (dHvA) effect. From the results of the dHvA experiment for LaIrSi 3 , the Fermi surface is found to split into two Fermi surfaces due to the spin–orbit interaction arising from the non-centrosymmetric crystal structure, which are separated by about 1000 K. Similar split Fermi surfaces are expected in the antiferromagnet CeIrSi 3 . The electronic state of CeIrSi 3 is tuned from the antiferromagnetic state to the superconducting state by applying pressure. The upper critical field H c2 (0) at a pressure of 2.65 GPa is found to be highly anisotropic: H c2 (0)=95 kOe for H ∥[110] and H c2 (0)≃300 kOe for H ∥[001], with the superconducting transition temperature T sc ≃1.6 K. The large magnitude and anisotropy of H c2 (0) in CeIrSi 3 are consistent with the theoretical prediction for superconductivity in the non-centrosymmetric crystal structure. Superconductivity is also observed at ambient pressure in CeIr 1- x Co x Si 3 .