Magnetic structures of CeMg3, NdMg3 and CeInAg2

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.