Synthesis and properties of Ba3NaRu2O9-δ and Ba3(Na, R)Ru2O9-δ (R=rare earth) crystals

Abstract Crystals of Ba 3 NaRu 2 O 9− δ ( δ ≈0.5) and Ba 3 (Na, R)Ru 2 O 9− δ (R=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) were grown by an electrochemical method, and their crystallographic, magnetic, and electric properties were studied. All crystals have a hexagonal structure of space group P 6 3 mmc . Ba 3 NaRu 2 O 9− δ and Ba 3 (Na, R)Ru 2 O 9− δ (except Ce) have a negative asymptotic Curie temperature suggesting the existence of an antiferromagnetic order; however, they are paramagnetic at temperatures above 1.7 K. Ba 3 NaRu 2 O 9− δ has an effective magnetic moment P eff of 0.91 μ B , while P eff of Ba 3 (Na, R)Ru 2 O 9− δ (except Ce) reflects the large free-ion moment g J(J+1) of the rare earth ions. Ba 3 (Na, Ce)Ru 2 O 9− δ shows peculiar magnetic behavior that differs from the magnetism of other Ba 3 (Na, R)Ru 2 O 9− δ crystals. The resistivity of all crystals exhibits an activation-type temperature dependence with an activation energy in the range of 0.1∼0.2 eV.