Magnetic structures of CeMg3, NdMg3and CeInAg2

Abstract

The authors have performed neutron diffraction experiments on CeMg₃, NdMg₃ and CeInAg₂ intermetallic compounds. The crystallographic structure of CeInAg₂ is shown to be of the Heusler (L2₁) type. CeMg₃ and CeInAg₂ order antiferromagnetically at 4 and 2.5K respectively; the magnetic ordering of the face-centred cubic cerium array is the first antiferromagnetic type. NdMg₃ orders at 6K, the antiferromagnetic structure is the second type like TbMg₃. The ordered moments for CeMg₃ (0.59 mu _B at 2K) and NdMg₃ (1.30 mu _B at 2K) are smaller than those calculated from a simple Hamiltonian including crystal field and isotropic exchange. This reduction may arise from a contribution of the conduction band, which in the cases of CeMg₃ and CeInAg₂ leads to the appearance of a Kondo effect revealed by the behaviour of electrical resistivities.