High temperature expansion and exact diagonalization of the rhodium nuclear spin system compared to experimental results

The nuclear spin System of Rh metal has recently been investigated experime ntally. Aro nuclear magnetic ordering was observed in these measurements, i n spite of the very low nuclear entropy achieved. To study this system theo retically, we have applied the method of exact diagonalization to a 16 spin I=1/2 fee cluster with both Ruderman-Kittel and dipolar interactions. In t his work. we compare the results of this method with the experimental data and the high temperature expansion results in the paramagnetic state. The h igh temperature expansions agree with the experimental data down to 1 nK, w hile the exact diagonalisation results are less accurate.