Magnetic Properties of RCoGe3 (R: Ce, Pr, and Nd) and Strong Anisotropy of the Upper Critical Field in Non-centrosymmetric Compound CeCoGe3

We grew single crystals of RCoGe 3 (R: La, Ce, Pr, and Nd) by the Bi-flux method, and studied the magnetic properties of PrCoGe 3 and NdCoGe 3 and the pressure-induced superconducting property of CeCoGe 3 . These compounds crystallize in a non-centrosymmetric tetragonal structure. PrCoGe 3 and NdCoGe 3 were found to be a paramagnet and an antiferromagnet with the Neel temperature T N = 3.8 K, respectively. Crystalline electric field (CEF) schemes were proposed for PrCoGe 3 and NdCoGe 3 . The magnetic property of a pressure-induced superconductor CeCoGe 3 is highly different from those of PrCoGe 3 and NdCoGe 3 , or a similar pressure-induced superconductor CeIrSi 3 . This was discussed in connection with the superconductivity of CeCoGe 3 . We clarified the upper critical field H c2 for H ∥[001] and [100] by measuring the electrical resistivity under pressure P in magnetic fields: H c2 (0) ≃24 T for H ∥[001] and H c2 (0) ≃3.1 T for H ∥[100] at 0 K at P = 7.1 GPa. A huge H c2 (0) value for H ∥[001] is a comb...