Investigations of the magnetic properties of CeRh2Si2 using lattice parameter, LIII edge and extended X-ray absorption fine structure measurements

The lattice parameters of tetragonal CeRh2Si2 are anomalous compared with those of the other members of the series CeM2Si2 (M ≡ Ru, Rh, Pd and Ag). Measurements of the susceptibility of CeRh2Si2 as a function of temperature in the range 15–300 K reveal interesting features. At high temperatures the susceptibility obeys a Curie-Weiss law with an effective moment per cerium ion that is 20% higher than that of the free Ce3+ ion. There is a cusp-like peak at about 37 K and a relatively smaller peak at 5.2 K. The lattice parameters a and c show a slight decrease between 300 and 40 K and a rather small increase between 40 and 12 K. The LIII absorption edge and the extended X-ray absorption fine structure spectra are unchanged between 20 and 300 K. This clearly indicates that the valence of the cerium ion does not change and that the first-nearest-neighbour environment (eight rhodium atoms and eight silicon atoms) of the cerium ion is not affected by the transition at 37 K.