Electrical and Magnetic Properties of R3Al11 (R = La, Ce, Pr, and Nd)

High-quality single crystals of R3Al11 (R = La, Ce, Pr, and Nd) with the La3Al11-type orthorhombic crystal structure (space group Immm) have been grown by the Al-flux method. For Ce3Al(11), signatures for ferromagnetic and anti ferromagnetic orderings at T-C = 6.3 K and T-N = 3.2 K, respectively, have been observed in the magnetic susceptibility, magnetization, specific heat, and electrical resistivity. An anti ferromagnet Pr3Al11, on the other hand, exhibits two magnetic transitions at T-N1 = 12.6 K and T-N2 = 3.1 K. An antiferromagnet Nd3Al11 also exhibits multiple magnetic transitions at T-N1 = 13.2 K, T-N2 = 9.4 K, T-N3 = 2.9 K, and T-N4 = 1.77 K in zero magnetic field. The transition at T-N4 has a first-order character. The crystalline electric field (CEF) analysis of magnetic susceptibility, magnetization and specific heat data shows that the CEF splitting is larger for Ce3Al11 than for Pr3Al11 and Nd3Al11. The CEF ground state of Pr3Al11 is a singlet. Magnetic order occurs in this compound owing to the exchange mixing of the CEF around state and low-lying excited states. The ferromagnetic like component of the magnetization for H parallel to [010] is characteristic of R3Al11 (R = Ce, Pr, and Nd), which is most likely due to the Dzialoshinsky-Moriya interaction for two nonequivalent R atoms.