Magnetic properties of RCuAl3 (R = Pr and Nd) compounds

( )Magnetic properties of PrCuAl3 and NdCuAl3 single crystals, adopting the tetragonal BaNiSn3 -structure-type, are reported. Our magnetization and specific heat measurements revealed no magnetic ordering in PrCuAl3, while NdCuAl3 orders antiferromagnetically below T-N = 2.45 K. The paramagnetic regime was investigated for both analogues revealing (i) the a-axis as the easy direction of magnetization with (ii) a relatively high uniaxial anisotropy energy of 13.2 meV for PrCuAl3 compared to a smaller value of 4.7 meV for NdCuAl3. The measured data are well explained by rare-earth ground state multiplet splitting in crystal electric field. A powder neutron diffraction experiment confirmed PrCuAl3 to remain paramagnetic down to 1.5 K. On the other hand, NdCuAl3 orders antiferromagnetically below T-N with an incommensurate magnetic structure described by two propagation vectors k(1) = (1/3 - delta(1), 0, 0) and k(2) = (1/7 - delta 2 , 1/7 - delta(2) , 0), where delta(1) = 0.035(1) and delta(2) = 0.007(1). The magnetic moments (of both magnetic modulations) are arranged within the basal plane with a small z-component moment allowed by the symmetry. Our results are discussed with respect to other RCuAl3 compounds. (C) 2018 Elsevier B.V. All rights reserved.