Anomalous magnetic exchange interactions in SmCu2 - art. no. 134405

RCu2 compounds (R=rare earth) show magnetic structures with very different propagation vectors. This behavior can be explained by the anisotropy of th e magnetic exchange interaction in combination with the crystal field. In o rder to support this model the magnetic phase diagram of a SmCu2 single cry stal has been investigated by magnetization, thermal expansion, magnetostri ction, electrical transport, and specific heat measurements. The magnetic s tructure in zero field has been determined by neutron diffraction on a powd er sample using Sm-154. The magnetic moments were found to be oriented para llel to the b direction in contrast to other RCu2 compounds (R=Tb, Dy, Ho) with the same propagation. In order to explain the observed magnetic struct ure of SmCu2 we infer that the anisotropic part of the exchange interaction tensor is reversed in comparison with the other RCu2, compounds.