Metallic conductivity and a Ca substitution study of NaRh2O4 comprising a double chain system

Abstract The metallic compound NaRh 2 O 4 forms a full range solid solution to the insulating phase CaRh 2 O 4 . At a Na concentration of 0.25 mole per formula unit, we found an unexpected contribution to the specific heat at low temperature [K. Yamaura, et al., Chem. Mater. 17 (2005) 359]. To address this issue, specific heat and AC and DC magnetic susceptibilities were additionally measured under a variety of conditions for the Na 0.25 sample. A new set of data clearly indicate the additional specific heat is magnetic in origin; however, the magnetic entropy is fairly small ( ∼ 1 % of Schottky term for a simple splitting doublet), and there is no other evidence to suggest that a magnetic phase transition is responsible for the anomalous specific heat.