A Study of the Magnetic and Thermal Properties of Ln3RuO7 (Ln=Sm, Eu)

Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln3RuO7 (Ln=Sm, Eu) have been investigated. For Eu3RuO7, a magnetic transition due to Ru5+ ions is found at TN=22.5 K on the susceptibility–temperature curve. Specific heat measurements also exhibit a LAMBDA-type anomaly at the same temperature. The M?ssbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm3RuO7, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru5+ ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm3+ ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu3RuO7 and Sm3RuO7, respectively. The results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.