MAGNETIC-SUSCEPTIBILITY OF SM2IN - THEORY AND EXPERIMENT

R(2)In (R=Rare-earth) compounds form an isostructural (P6(3)/mmc) seri es in which different kinds of magnetic order can be encountered depen ding on the nature of the rare-earth ion. Among them, Sm2In is the onl y one to order in a ferrimagnetic structure (T-C=150 K) as deduced fro m magnetic susceptibility measurements. In this paper, the physical pr operties of Sm2In are investigated as a function of temperature and co mpared with the Neel model modified to take into account the Van-Vleck nature of the magnetism associated with the Sm3+ ions. The coupled me an field equations for the magnetizations of both sublattice are solve d self consistently for a matrix hamiltonian of dimensions 66X66 corre sponding to the truncation of the Hilbert space to the set of (2L + 1) (2S + 1)=66 basis functions for the H-6 manifold of the Sm3+ ion. An o verall agreement between theory and experiments is achieved for T>40 K , leading to the first estimate of the exchange parameters for this ma terial.