Magnetic frustration in partially ordered double perovskites Ln3Ni2RuO9 (Ln = La, Nd)

Abstract Ln3Ni2RuO9 (Ln = La, Nd) oxides (prepared by a solid state metathesis route) adopt a monoclinic (P21/n) A2BB'O6 double perovskite structure wherein the two independent octahedral 2c and 2d sites are occupied by Ni2+ and (Ni2+1/3Ru5+2/3) cations, respectively. In contrast to the expected ferromagnetic behavior, Ln3Ni2RuO9 oxides show a spin-glass behavior without long range magnetic order down to 2 K. These results reveal the importance of competing nearest neighbor (NN), next nearest neighbor (NNN) and third nearest neighbor (third NN) interactions between the magnetic Ni2+ and Ru5+ ions in the partially ordered double perovskite structure that conspire to thwart the expected ferromagnetic order in these materials.